In my mind the question should also be how much can your manager approve via credit card without anyone expecting a business case to support the purchase.

In my case I regularly approve hundreds of thousands dollars for other people, but I generally have everything of mine approved credit card or not. What's important is that if I can justify if to my manager and if it's under 5k then it requires only a conversation, but over 5k I'm writing business cases and having all kinds of scrutiny and less chances to compete for budget $.

May seem strange, but using the 5k amount has always seemed like a loop hole. I've seen data vendors sell data for just under 5k every month otherwise the annual wouldn't even be considered. I generally find them and end up shutting them down or using the monthly costs as a business case to make data purchases in full just to save money.