Marketplace sync, Channel Advisor vs Codisto vs custom?

Three real options at different price points:

Channel Advisor (now Rithum): enterprise marketplace integrator. Magento extension, syncs inventory + orders + listings to Amazon, eBay, Walmart, Newegg, Wayfair, Google Shopping. Strengths: bulletproof at $100M+ GMV, mature dispute / reconciliation tools, repricer included. Weakness: enterprise pricing, $30k, $200k/yr depending on GMV. Pick at >$10M marketplace GMV.

Codisto (now Shopify-owned but still has Magento connector): mid-market. Real-time inventory + order sync, listing builder, decent multi-region support. $200, $2,500/mo depending on plan + SKU count. Weakness: Newegg + Walmart support is thinner than Amazon/eBay. Pick at $1M, $10M marketplace GMV.

M2E Pro (free + paid editions): Magento-native open-source extension. Free for Amazon/eBay basic, $500, $2k/yr for advanced features. Strengths: deep Magento integration, no per-SKU fees. Weakness: needs more in-house ops attention than the SaaS tools. Pick at <$1M marketplace GMV with in-house Magento expertise.

Custom (direct API): build directly against Amazon SP-API + eBay API. Justified only at >$50M marketplace GMV with weird requirements (multi-account, complex SKU mapping, custom repricer). Build cost: $80k, $200k. Don’t pick this lightly.