Amazon Business + Walmart marketplace sync from Magento, how?

Magento as the order-of-record, marketplace as a sales channel. For B2B packaging the relevant marketplaces are Amazon Business (B2B-only buyer pool, tax-exempt sellers, quantity-discount pricing), Walmart Marketplace (B2B section growing fast), eBay Business Supply, and increasingly Faire for indie boutique buyers.

Three integration patterns:

• Channel manager (Channel Advisor / Codisto / Sellbrite / Akeneo PIM), PIM/feed-based. Master catalog in Magento (or in PIM upstream), channel manager syncs product feeds out + order feeds in. Best for > 3 channels. Cost: ~$400, $2,500/mo.
• Direct API per channel, Amazon SP-API, Walmart Marketplace API, eBay Trading API. Cleaner long-term but each channel is ~$8k, $25k of dev work.
• App-level extensions, Magento Marketplace has Amazon connector, eBay connector. Cheapest, but lowest-quality for packaging (poor variant handling, no GTIN auto-population, no marketplace-category mapping).

Packaging-specific marketplace gotchas:

• Case-pack SKU mapping, Amazon treats a "25-pack of boxes" as one ASIN, not 25. Your Magento SKU "25-case" maps to the parent ASIN, not the unit-box ASIN. Common mistake.
• Quantity-discount visibility on Amazon Business, Amazon’s tier-price API is its own beast; tier-price sync from Magento needs special handling.
• Inventory of truth, pick one. If Magento → push to channels. If a PIM (Akeneo, Pimcore) → push to both Magento and channels. Mixing creates the "why is the SKU oversold?" chaos most distributors hit at $5M+.