Collectible secondary market, used / open-box / loose-figure listings with condition grading?

The pattern works for Funko Pop, Hot Toys, Sideshow, Pokemon graded slabs (PSA, BGS), MTG singles, sealed wax, vintage Lego.

Magento architecture:

• Used / open-box / loose listings as separate Magento simple products, linked to the master SKU via a custom relation attribute. Each listing has its own price, condition, photos, and inventory of 1.
• Condition grading attribute, Mint / Near Mint / Very Good / Good / Acceptable. For graded collectibles (PSA, BGS, CGC) the slab number + grade is a custom field.
• Photo upload per-listing, each used item needs photos. If you sell in volume, PIM-driven (Akeneo / Pimcore) with mobile-app photo capture. Otherwise admin grid upload.
• Buy-back flow, customer initiates trade-in (form: condition + photos + master SKU lookup), gets quoted store credit (60-70% of resale value typical), ships item, you grade on receipt, store credit auto-issued via Magento store credit module. Cuts inventory acquisition cost ~30-40% vs. wholesale buy.
• Market price sync, eBay sold-completed API for Funko + collectibles, TCGplayer market price API for Pokemon TCG + MTG singles. Cron job nightly re-prices used listings within a +/-5% band of market. Manual override for premium grade.

Inventory model: each used item is a quantity-1 SKU. Don’t share inventory with the new-mint master, you’ll oversell on the listing that’s actually a unique item. Use Magento parent-child product relation for the master-to-used mapping if you want PDP-level cross-selling ("buy mint $48 / buy used very-good $32").