There's no such thing. There are no rules to pricing your cards. Why, you could sell them for 50 if you want. (If you would, contact me first) Just pick the price you're comfortable with, or based on your need for clintz. If you really need clintz, then lower your price and someone'll buy it off you sooner. If you feel like showing off your collection, then sell them for 1 billion so that when people look into your profile, they will see your cards for sale.
Just look at the min price listed. The lowest amount on said card is usually what you will sell for. If someone buys say 100ricos and his price jumps from 50clintz to 10000clintz you better sell fast and not wait a week. There are exceptions as some cards are used unevolved like most of the pussycats cards. Their level 1-4prices will be more expensive then their last level price.
New blood cards are always really expensive their first two weeks out but will drop and then rise alittle down the line.