Trading with Dealers at Card Shows?

[Snapolit1]

I've never been a trader.

I don't know how you trade without being cognizant of market value (comps).

If my card just sold for $500 last week, and your card sold last month for $300, why would I trade you a $500 card for a $300 card? Wouldn't it make sense to sell my card for around $500 and try to find the other card for around $300. And pocket the rest?

Maybe the comps are stale and unreliable for obscure stuff like Leon references above. Or maybe in thinly sold cards you will do anything to grab something. Or maybe people just want to make a trade for the sake of making a trade because it feels fun. A few people on BST have approached me about trades and it typically goes like this:

My card/photo is for sale for $2000.

Hey would you be interested in any of these?

I look and "these" are worth (based on comps) like $1000.

Nah, not really looking for a trade.