Buying the Mona Lisa for $200m is not at all the same thing as netting a $200m profit.
Better analogy: you buy a big museum collection that contains some lost Rembrandt paintings, widely regarded as his worst, but still considered valuable because it's Rembrandt. You think you might have a hard time selling them, so you look up their original purchase price and find that it was $1 million, so you burn them instead and claim a $1 million writeoff, for a guaranteed $250k decrease in taxes for essentially 0 additional cost, resulting in $250k of extra profit.