Cost + timeline for an electronics platform migration to Magento?

Realistic ranges by SKU + complexity tier:

Tier 1: 2k–10k SKUs, single warehouse, B2C-only, Amazon only

• Build: 10–14 weeks. Cost: $35k–$70k.
• Stack: Magento Open Source + Hyvä + M2E Pro (marketplace) + Mirasvit RMA + simple PIM (or no PIM if catalog stable).

Tier 2: 10k–50k SKUs, 2–3 warehouses, 20–40% B2B share, Amazon + eBay

• Build: 14–20 weeks. Cost: $80k–$160k.
• Stack: Magento Open Source + Hyvä + Codisto (marketplace) + Akeneo PIM + Aheadworks/Mageplaza B2B + Mirasvit RMA + MSI configuration.

Tier 3: 50k+ SKUs, 4+ warehouses, >40% B2B distribution, Amazon + eBay + Newegg + Walmart

• Build: 20–32 weeks. Cost: $180k–$400k.
• Stack: Adobe Commerce (native B2B) or Magento OSS + Aheadworks B2B suite, Hyvä, Channel Advisor (marketplace), Akeneo or Pimcore enterprise, Mirasvit RMA + Extend warranty integration, custom MSI source-selection algorithm, ERP integration (NetSuite / SAP).

Hidden costs to budget for: (1) data migration from current platform — $5k–$25k depending on data quality; (2) URL redirect map — critical for SEO continuity, $3k–$10k; (3) ERP / OMS integration — $15k–$80k; (4) ongoing retainer — $2k–$10k/mo for keeping the stack patched + iterating.

I quote fixed-fee for Tier 1 + Tier 2; Tier 3 is time-and-materials with weekly check-ins because surprises are inevitable.