Not to mention, the $5B tax break isn't money lost, it's merely an opportunity cost. If HQ2 wasn't moving to this city/state, they'd still be out that money.
It isn't "merely an opportunity cost." Putting up with Amazon's HQ2 will significantly increase local infrastructural load and therefore costs. It is explicitly reducing their revenue while increasing expenses and there's no reason to assume--it's possible but the assumption is dangerous--that there will be sufficient compensatory side-effect revenues to be worth the transaction.