Also you're taking a gamble by challenging the IRS to buy something at a discount that they won't actually call your bluff and you lose out on money. And if you're actually standing by your personal assessment over theirs, you either make money or you get to skip the tax bill.
This seems like a much better balance than what we currently have.
If they can't sell the asset and then return 80% of it's market value to the original owner over the course of a year, than they were probably wrong about the market value.
Of course there are certain items that may take longer than a year to find the right buyer, mega yachts, specialized works of art, but if these things take years to sell and find the right buyer than their potential market value should be reduced to reflect that.
It's like telling any appraiser... Yeah you think it's worth that much? Prove it! Buy the sucker! If you did that multiple times they would go bankrupt, because sure they may be able to resell the thing if priced correctly but they need to pay for it in the first place. And to do it at the scale of IRS ... It's not a reasonable request or expectation.