Wayfair, Amazon Beds, Costco, how do you connect Magento to mattress marketplaces?

Mattress brands sell across 3 marketplaces in addition to DTC, and each one has its quirks. Magento as the order-of-record, marketplace as a channel:

• Wayfair, the dominant home-goods marketplace for mattresses (Wayfair owns Joss & Main, AllModern, and Birch Lane in the bedding segment). Integration via Wayfair’s CastleGate fulfillment program or direct EDI. Wayfair pays ~75% of retail, takes care of returns, but takes margin and demands fast ship-out (under 48 hours). Magento integration is EDI-based or via channel manager (Channel Advisor, Codisto).
• Amazon Beds (Amazon’s mattress category), high volume, low margin, customer-acquisition channel. Tuft & Needle and Linenspa built brands almost entirely on Amazon Beds. Integration via Amazon SP-API + FBA for queen-and-under (boxed); king + cal-king ship from your warehouse directly. ~$8k, $15k of dev for a clean Magento ↔ Amazon SP-API integration; channel managers like Codisto / Channel Advisor handle it at ~$400, $1,500/mo.
• Costco, mattress-in-a-box and full mattress lines. Costco demands EDI integration + co-branded packaging + a Costco-specific SKU that maps to your master SKU in Magento. Annual contract, very high volume, very low margin. Casper sold Costco hard in 2018-2019 as a CAC channel before the IPO.

For mattress brands at $5M+ GMV, a channel manager (Channel Advisor or Codisto) is usually the right call, managing 3 marketplaces + DTC by hand without one is the “why is my king oversold on Wayfair?” chaos. Inventory of truth lives in Magento, channel manager syncs out + brings orders back.