What an ecommerce replatform actually costs in the UK in 2026

Ask three agencies to quote the same migration and the numbers can land a factor of five apart. That is not because two of them are trying it on. A replatform quote prices work that never shows up on the storefront, and each agency has scoped a different amount of it. The owner sees a shopfront and a monthly platform fee. The real project is underneath, in the data, the integrations and the rebuild, and that is where the money and the risk actually sit. Everything below is aimed at one thing: helping you read a quote for what it really contains, rather than what it says on the front page.

The honest ranges

There is no single price for a replatform, because the word covers everything from a two-week theme swap to a nine-month headless rebuild. What follows is grouped by how complex your store actually is, which is the thing that moves the number, rather than by the platform badge. The ranges assume a clean, safe cutover onto Shopify or Shopify Plus, which is the most common UK move in 2026.

The gap between the rows is not linear, and that catches people out. A simple store with a thousand plain products and a couple of integrations is a contained piece of work with a fairly predictable number. A complex store is not just a bigger version of that. Custom pricing rules, a B2B layer, an ERP that has to stay in sync, years of order history and a catalogue built on bundles and variants each add their own risk, and risk is what a budget is really paying for. Two stores on the same revenue can sit in different rows entirely, which is the first sign that revenue is the wrong ruler.

The timelines look long until you see what fills them. Little of a migration is spent building the new theme. Most of it goes on moving and reconciling data, rebuilding each integration, testing the cutover on a staging copy, and then watching the first fortnight of real traffic. For the specific and common case, a Magento to Shopify migration in the UK typically runs £30,000 to £120,000 and takes 8 to 16 weeks for a clean cutover [1]. If a quote for a real store with real history comes in dramatically under the bottom of that range, the gap is rarely a bargain. It is usually scope that has not been priced yet, and you will meet it later as a change request or a broken cutover.

Why the platform licence is the cheap part

Here is the part owners are least prepared for. On a mid-market replatform the platform licence is only 20 to 40 percent of the total; implementation, data migration and integration work make up the rest [2]. The Shopify Plus fee itself is around £1,800 a month on a three-year contract [4], which is a real cost, but it is not where a replatform budget goes. You are buying a rebuild, not a subscription, and the subscription is the line you can read most easily, which is exactly why it draws the eye and the platform underneath it does not.

This is why comparing quotes platform-by-platform misses the point. When two agencies quote the same job at very different numbers, you are not comparing Shopify against Shopify. You are comparing how much data and integration work each one has actually written down. The honest quote and the optimistic quote diverge precisely on the lines an owner finds hardest to read, which is why the next two sections matter far more than the sticker price. Learn to read those lines and the whole exercise gets less frightening, because you can finally see which number is describing the real job.

What actually moves the number

Revenue is the instinctive way to size a project and it is the wrong one. After reviewing published agency rate cards, the pattern is blunt: store complexity, not revenue, drives most of the price variation, and catalogue size plus custom integrations predict the final cost far more reliably than a revenue tier does [6]. Four drivers do most of the work, and it is worth knowing them by name so you can find them in a quote.

✦AI generated

Data volume and catalogue complexity

Moving fifty simple products is trivial. Moving fifty thousand products with size, colour and material variants, custom metafields and high-resolution media is a genuine data-engineering task [1]. It is not the row count alone that hurts, it is the shape of the data. A store with five hundred products that use bundles, customer-specific pricing and years of order history is harder to move than one with two thousand plain products and a clean recent history.

This is why a good agency asks detailed questions about your catalogue before it quotes: how many products, how many variants, what lives in metafields, how much media, how many years of orders you need to keep. When those questions come early, that is diligence, not a stall. A quote that arrives without them has guessed at the hardest part of the job, and a guess on the biggest line is the whole reason two quotes for the same store can differ so much.

What has to be mapped, not just copied

Magento and Shopify do not store the same things the same way, so most of a migration is mapping rather than copying. Products, variants, metafields, customer records, orders, media and URL redirects all have to be re-shaped into how the new platform expects them [1]. Some of it moves through a structured export and import. Plenty of it does not, and needs custom scripting to preserve meaning rather than just move rows. The phrase to be wary of is that it is just an export and import, because the export is the easy twenty percent; the reconciliation, the edge cases and the validation are the rest, and they are where a migration quietly grows or quietly breaks.

Integrations, the biggest swing after data

Every system your store talks to is a rebuild on the new platform. Your ERP, PIM, payment gateway, shipping and fulfilment, CRM and email each connect differently to Shopify than they did to Magento, and each is a separate line of scope [6]. This is the single biggest swing factor after data, and it is the one most likely to be quietly under-scoped, because an agency that has not asked for a full list of your integrations cannot have priced them. Count your integrations before you read a quote, then check that every one of them is named in it. A missing integration is not a saving, it is a change request waiting to happen at the worst possible moment, which is the week of go-live.

SEO preservation

A migration is the easiest place in the world to lose your search rankings, and the cheapest place to protect them if you do it on the way through. It means a complete old-URL to new-URL redirect map and structured-data parity, so the new store presents the same signals to Google that the old one did. Done properly it is a modest line. Skipped, it shows up six weeks later as a fall in organic traffic that costs far more than the redirect work ever would have, and it is the kind of loss that is slow to notice and slow to recover.

The costs most quotes leave out

The sticker price is rarely the real price, and the difference is not padding. It is a set of costs that are predictable enough to plan for and are still routinely left off the first quote. Budget for these or be surprised by them, and be aware that most of them are not optional extras but ordinary parts of any real cutover.

None of these is exotic. Dual-running and post-launch stabilisation in particular are not risks that might happen, they are near-certain parts of any real cutover, and a quote that omits them is describing a demo rather than a migration. The one genuinely optional line is data cleanup, and it is the one worth keeping, because the alternative is paying to move a mess that you will then pay a second time to fix. If you only add one thing to a quote you have been handed, add the contingency; if you add two, add the fortnight after go-live.

How to sanity-check a quote before you sign

You do not need to be technical to pressure-test a migration quote. Four questions separate a finished quote from an optimistic one, and the answers tell you as much by their shape as their content. If a question is met with a vague reassurance rather than a line on paper, treat the vagueness as the answer.

The bottom line

Judge a replatform by how seriously its quote treats data and integrations, not by the platform on the badge or the monthly fee. The store that gets migrated cleanly is almost always the one whose budget was honest about where the money actually goes, which is underneath the storefront, in the parts the owner cannot see. A number that looks too good next to the others is not usually a better deal. It is usually the same job with the hard, invisible sixty percent left unpriced, and that sixty percent does not go away because it was left off the quote. It arrives later, with less goodwill and less budget left to absorb it.

If you are weighing a replatform and want a second read on a quote before you commit, that is exactly what a build and migration review is for. We look at what has been scoped, what has not, and what it will really take to move your store cleanly, so the number you sign is the number you pay.