I think Nascar uses this system to discourage undervaluing entries: owners declare a value for their car, and Nascar has the right to buy the car at that valuation. They would only do this if the car was under by a significant margin, so there's a huge incentive to give a fair estimate for the car.

Its also a little similar to a system used to resolve splitting a 50/50 owned company: the person who wants to buy out the other partner must first give the price they'll pay, and then the second partner must choose between buying them out at that price, or selling their share.

Guatamala tried the reverse of that--they paid Chiquita chiquita's declared tax value for their land... pennies per acre. The US overthrew their democratically elected government over it.

Or to report the tax payment to the day some corrective law makes the item possible to sell, should it happens.

Of course, there can be an immediate arrangement if they just give away the item to a museum.

Give people the option to sell art at an arbitrary percentage of a made-up valuation? I'm sure that would end well...

The last thing the government wants to be involved with is selling real estate, art and other illiquid assets. There is a very real possibility that the government would lose money if it is unable to sell the asset at the original valuation.

Well the reality right now isn't too different. Ignoring the bald-eagle situation, they sell some of the items to pay for the tax bill, and keep the remainder.

The government wants cash, it has no use for paintings!