whats the most you would pay for a card

If you are looking to sell cards, it would depend on whether or not they would want the card for resale.

Card value can be anywhere from 5 cents to $80,000. But usually you're paying less than 50¢ for uncommons and around 1-5 dollars for rares. The super expensive cards are usually around 10-20 dollars. Doesn't usually go much higher than that.

Is a full art black zekrom rare? (Pokeman)

For me personally it would depend on the artist & the year the set of Cards I was trying to complete. For a set of Olivia 1990 - 2000 $5.00 & up depending if it's rare, hologram $20.00ish - rare ? X- Men - I have 2 complete sets - $ 0 SuperMan - 2 set $ 0

We buy cards using the Star City buy-in guide. We match their price for store credit and usually do 80% of that for cash. We'd buy up to $50,000 a month.

If you're looking to sell cards, they usually give you 40-60% of what they plan to resell it for in store credit, or 80% of their buying price in cash. So really I wouldn't recommend selling it to the most game stores unless you can't sell your eBay listing.