A replatform quote tells you the headline number, not the real one. The build cost is what agencies compete on, so it gets sharpened, while the surrounding costs that determine the true total, SEO recovery, extension repurchases, data validation, training, often go unmentioned until they arrive. None of these are hidden because anyone is being dishonest. They are hidden because they are easy to leave out of a sales conversation and painful to add back in once the project is underway.
The base numbers are already significant. A Magento to Adobe Commerce migration typically runs $100,000 to $350,000 or more, according to migration cost analysis from IWD Agency, and that is before the line items below. Budgeting for the full picture, not just the build, is the difference between a replatform that lands on plan and one that quietly costs 30 percent more than anyone said.
What does the SEO and redirect work really cost?
The most underestimated cost is the 301 redirect map and SEO recovery, because URL structures usually change in a replatform and every changing URL needs a redirect to preserve rankings. Brands that skip or underinvest in this can lose a large share of organic traffic for months, which is a revenue cost that dwarfs the line item it would have taken to do it right. The redirect map is tedious, detailed work, mapping old URLs to new ones, and it is exactly the kind of task that gets compressed in an optimistic quote.
Recovery has its own tail. Even with clean redirects, search rankings often dip temporarily after a replatform, so there is a period of reduced organic traffic to plan around financially, plus the work of resubmitting sitemaps and preserving metadata. Treating SEO continuity as a first-class part of the migration data and continuity plan, with real budget attached, is how you avoid trading a successful technical migration for a six-month organic-traffic crater.
What about extensions, integrations, and data?
Extensions, integrations, and data validation are recurring hidden costs because each carries work the build quote tends to assume away. Extensions often need to be repurchased or rebuilt on the new platform, and replacing a stack of them can add a meaningful sum on its own. Integrations to ERP, PIM, and other systems have to be re-established and tested, and each named integration is real engineering, not a checkbox. These are not edge cases; they are the normal substance of a replatform.
Data is the quiet one. Migrating customers, orders, and catalog is not just moving records, it is validating that every dataset transferred correctly, with matching row counts and working sample records, which takes real QA time that a thin quote omits. Skimp on it and you ship silent data loss to production. The honest way to surface all of this is a discovery phase before the number is set, the same audit that keeps a project on budget, so the extensions, integrations, and data work are priced as what they are rather than discovered at week ten.
How do you budget for the full picture?
You budget for the full picture by insisting on a discovery phase, asking explicitly what is excluded, and reserving a contingency for the surrounding work. The single best protection is discovery: a real audit of the store before committing to a price turns the hidden costs into known ones, so the quote reflects the whole project. An agency that resists discovery is one whose number you should trust least.
Then ask the uncomfortable questions directly. What is explicitly excluded from this quote. Is the redirect map included, and the SEO recovery period accounted for. Who pays to repurchase or rebuild extensions. Is data validation scoped as real QA or assumed. How much training and post-launch support is included. Add a sensible contingency on top, because even a thorough plan meets surprises. A replatform budgeted this way, build plus the real surrounding work plus a buffer, lands where it should, and the partner willing to walk you through all of it is the one giving you a true number rather than an attractive one. That candor is itself a sign of a serious Magento and Adobe Commerce team.
