Operator context
Longer answer
The cost range reflects real variance across the $5M-$50M brand band. SKU count, B2B Edition presence, custom extension count, subscription tenure, and multi-store complexity each move the cost meaningfully. A clean $5M B2C migration lands near $60K; a $40M migration with B2B, subscriptions, and multi-store complexity lands near $220K. Both are normal at their respective brand profiles.
Workstream-level breakdown for a typical $5M-$50M engagement: discovery ($8K-$25K), data migration ($15K-$60K), theme rebuild ($15K-$70K), app re-implementation ($8K-$30K), SEO migration audit ($8K-$40K), iPaaS if applicable ($10K-$50K annual), project management ($6K-$25K).
Hidden costs operators routinely under-budget: internal team time ($15K-$45K at loaded rates across the 14-26 week timeline), stabilisation extension ($10K-$30K beyond the build engagement), change orders ($10K-$50K for brands without discovery discipline), and post-launch tool subscriptions ($2K-$5K annually for the permanent stack).
Brands that ballpark their cost should start from the brand-size tier (look up the cost guide for source-platform-specific detail), add 15-25% contingency for variance drivers, and use that as the budget anchor for agency conversations. Actual quotes typically land within ±30% of this ballpark.