I think I remember hearing about a common trick of buying a painting, holding it for a while, getting it appraised by someone who deems that the value has gone up to a bigger amount, donating the painting, and then you get tax breaks based on the appraised value, even if that appraised value is much higher than anyone else is actually interested in paying.

Granted, I can't remember if you're supposed to actually be able to turn a profit by doing this trick, or if it just makes it a little cheaper for rich people who want to temporarily own fancy things.