The Appraise skill is counted as a skill based off the misunderstanding that objects have intrinsic value. In reality, objects are worth what the market will bear. D&D assumes a static market, so all you have to do is ask a shop keeping if they will pay x for a good. If they say no, you've asked too much. Walk this number down until willing to pay that amount and voila, no appraise check needed. This is not a theoretical excersize unless the DM allows you to find someone willing to pay more than the items (marketplace) value. Since this goes against what most people expect, it renders the appraise skill useless.
However the above IS useful to realize that maybe this mechanic is useful. What if the 'shopping around' for better buyers was the actual function of Appraise? This might allow selling an item at full market price. Suddenly Appraise is a useful skill again. This will steer certain classes to a higher WBL for DMs using treasure guidelines strictly. But since higher tier classes with the notable exception of the factotum, don't often have appraise as a class skill, this is actually helpful for balance.
If not using this skill, consider allowing classes with appraise to chose another class skill. A PC can successfully sell an object worth up to 400 times the ranks in appraise in gp. The DC to be made for each check is the full value of the object divided by (400 times the character's int mod).
