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Replatforming
What a replatform really costs: a line-by-line budget
By DEQIO · October 2026 · 6 min read
In short
The platform licence is typically only 20–40% of what a replatform costs, and the agency’s build quote misses several lines that every project pays for anyway. In our worked example, a £120,000 quote becomes about £295,000 of cash spend in year one, plus £60,000 of internal time. None of it is hidden on purpose. It just isn’t in anyone’s quote.
The headline numbers
A mid-market replatform typically costs about £110,000–£225,000 all-in and takes five to ten months (Elogic Replatforming Cost Index, 2026). The same index puts the licence at only 20–40% of total project cost. The rest is implementation, integration, data migration and testing.
The bigger point is that what you are moving away from drives the cost more than where you are moving to. A store with one ERP, 10,000 SKUs and light B2B is a different project from a single-site D2C store, whatever the destination platform.
Every line, and who usually forgets it
| Line item | What it covers | Usually in the agency quote? |
|---|---|---|
| Discovery | Requirements, integration inventory, data audit, redirect plan | Sometimes, often too thin |
| Design and front end | UX, templates, theme or headless front end | Yes |
| Build and customisation | Configuration, custom features, extensions | Yes |
| Integrations | ERP, PIM, OMS, payments, tax, search, email | Partly: “connector” priced, edge cases not |
| Data migration and clean-up | Products, customers, orders, content; fixing bad data first | Migration yes, clean-up rarely |
| SEO redirects | Mapping every old URL to its new one | Often a token line |
| Testing | Functional, integration, performance, UAT support | Partly; your UAT time is not |
| Go-live and hypercare | Cut-over, monitoring, 2–4 weeks of fast fixes | Often only the go-live day |
| Parallel licences | Old and new platforms both running for 1–3 months | No, it’s not their cost |
| Training and change | Teaching the team the new admin and processes | Rarely |
| Post-launch changes | The “now we can see it” list in the first six months | No |
| Internal team time | Your people on requirements, testing, data and sign-off | Never |
| Contingency | For what nobody knows yet | Never |
Two lines cause most overruns. ERP integration is the first: a pre-built connector might cost about £4,000–£22,000, but custom SAP or Oracle work can exceed £35,000 in year one. Data migration is the second: 64% of data migrations exceed budget, and overruns average 30% on cost and 41% on time (cited in the Elogic index).
Get the Replatform Decision Checklist
The questions to answer before you commit six figures.
A worked example
Take a UK retailer turning over £5m online, mostly direct-to-consumer with some trade accounts, one ERP and about 12,000 SKUs. Their preferred agency quotes £120,000 for design, build, a standard ERP connector, data migration and testing.
Here is what we would add before taking that number to the board. The figures are illustrative, built from published ranges, not a quote.
| Line | Basis | Amount |
|---|---|---|
| Agency quote | Design, build, connector, migration, testing | £120,000 |
| Proper discovery | If not in the quote; 3–4 weeks | £20,000 |
| ERP edge cases | Trade pricing, stock sync, order status beyond the connector | £25,000 |
| Data clean-up | Duplicate products, missing attributes, old customer data | £15,000 |
| Redirect mapping | Every indexed URL, checked after launch | £4,000 |
| Hypercare | Four weeks of priority fixes after go-live | £15,000 |
| Parallel running | Old platform licence and hosting for 2–3 extra months | £8,000 |
| Training | Admin, merchandising and customer service teams | £5,000 |
| Post-launch changes | 20% of implementation, first six months | £24,000 |
| Subtotal, external spend | £236,000 | |
| Contingency | 25% of external spend | £59,000 |
| Total cash, year one | £295,000 | |
| Internal time | 3–4 people at 20–40% for six months | about £60,000 |
The contingency is not padding. Elogic recommends 25–40% on any migration quote and treating it as an expected cost. We use 25% when discovery has been done properly, and more when it hasn’t.
What it costs to run, not just to build
Compare options over three years, not on the build quote. For each platform, add:
■ Licence. Shopify Plus, for example, starts at about £1,700 a month on a three-year term or £1,900 on a one-year term (billed in US dollars, so it moves with the exchange rate), and moves to a percentage of sales for higher-volume merchants (Elogic, Shopify Plus pricing). Adobe Commerce and Salesforce Commerce Cloud don’t publish prices; get quotes in writing.
■ Hosting (where it’s not included) and a CDN.
■ Apps and extensions: monthly app fees add up quickly on SaaS platforms.
■ Integration middleware subscriptions, if you use one.
■ Support retainer with your agency.
■ Upgrades: on self-hosted platforms, a significant upgrade roughly every three years.
Five questions to ask of any replatform quote
1. What assumptions is this quote based on? Ask for them as a list, because every one is a future change request.
2. Which integrations are fixed price, and which data flows are out of scope?
3. Who cleans the data, and what happens if it’s worse than expected?
4. What does hypercare include, and for how long?
5. What do you need from our team, in days, and when?
If the answers move the total by more than 20%, you don’t have a budget yet. You have a starting point. A Replatform Decision Review gives you costed options and a total cost of ownership for each, before you commit.
About DEQIO
Independent ecommerce leadership with 20 years on both the client and supplier side. No platforms, no builds, no referral fees. About DEQIO →
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