Actually, you would be suprised how much these things sell for. I am not one myself but I have been in some carder forums recently and have seen people selling COBs - full stolen identity for as little as 10$ each, and some selling credit card details ( with cvv number, which puts price up slightly) for as low as 1-2$.However, you are right in how much money they can extract from the cc's, one boasted on the forum that he could extract $500 from 1 european card in 20 hours...