You're misunderstanding how taxes are calculated. If they could deduct the writeoff, they'd make back their marginal tax rate times the purchase price, so they'

You're misunderstanding how taxes are calculated. If they could deduct the writeoff, they'd make back their marginal tax rate times the purchase price, so they'd still lose around $2B. (Similarly, when people deduct their mortgage interest, they don't get the mortgage "for free".)