Slab Swap: A marketplace exclusively for graded PSA, BGS and CGC slabs with price history charts, population data and seller ratings.

Seed the marketplace by hand-verifying the first 100 slab listings and charge a small commission per sale.

Why it can work: Graded slabs are the highest-value, lowest-dispute segment of the market, and buyers pay for price history and population data the big marketplaces do not surface well.