eBay

eBay remains the deepest open marketplace for comic books worldwide and is unavoidable as both a buying and selling channel for UK collectors. The Comics category covers everything from raw Bronze Age commons through CGC 9.8 modern keys to Golden Age pedigreed slabs. The volume of listings means that, for almost any non-trivial issue, you can find historical sold-price data within minutes by filtering Sold listings.

For research, that Sold filter is one of the most useful free tools available — it gives you actual realised prices (not asking prices) across multiple grades, holders and configurations, and is the primary input GoCollect, CovrPrice and similar services aggregate. Pair it with the Advanced Search options to filter by completed auctions only, exclude best-offer-not-accepted noise, and constrain by date range.

For selling, eBay's reach is unmatched but the fee structure and dispute system require attention. Use Authenticity Guarantee for slabbed comics over the qualifying value (currently £100 / $250 for raw, $750 for slabs in the US programme), which routes books through eBay's verification partner before they reach the buyer and significantly reduces fraud risk.

For UK buyers specifically, prefer UK-based sellers when possible to avoid customs duty surprises on books shipped from the US, and check the seller's feedback score on comic-specific transactions rather than overall numbers.