Comp

From BaseballCardPedia.com

Comp: Short for "comparison," a comparable sale or value of a similar baseball card. For example, if you're trying to determine the value of a specific card you own, you might look at recent sales of similar cards (in terms of player, card year, condition, etc.) to get an idea of its market value. Comps help collectors gauge how much their cards might be worth based on current market trends.