Heard it a few times and it certainly seems like something that would happen but is there any proof or real world examples?
Can an Appraiser just make something worth $20m based purely on their say so?
EDIT: Thanks some great replies! and yeah i was asking more about the tax evasion part than the 'modern art is bad lol' angle.
One thing I'll note about this is that art absolutely goes down in value and suffers from the same changes in taste as anything else. Markets get spiked, works get burned, artists aren't as trendy anymore. The really big names will usually pull in big money, but strip away the Sotheby's/Christie's hype machine and works are worth only what someone will pay for, and sometimes that's zero.