[cowkingdeluxe]

Not limited to art. It's easy to get a trusted appraiser for the wealthy. It is very difficult for the IRS to challenge.

Examples other than art: Company shares, real estate, time in certain contexts.

Edit: I'd like to point out GFischer's excellent summary on this https://news.ycombinator.com/item?id=18130720

[TAForObvReasons]

Computing too. Epic Games decided to make certain assets for the Paragon game free for use (with a black-box valuation), and it wouldn't be surprising if companies like google put a valuation on open source software that they released and took a deduction.

https://www.unrealengine.com/en-US/blog/epic-games-releases-...