The way budgeting works at Amazon, every team contributes items to lines in a spreadsheet. Those get rolled up at every level all the way to the CEO, who then approves or denies, and then it all rolls back down.

There is a special section called KTLO (keep the lights on). That one usually gets priority (because it's pro-customer, since customers want the existing stuff to keep working).

I've seen departmental budgets that dedicate 75% of their headcount to KTLO.