I've read that some people use a pre-paid credit card with a $1 spending limit when setting up their playground accounts. Seems like a reasonable approach.
They nerfed the $100 of AWS credits for Alexa developers with zero notice this month, which caused me to incur overages this and last month.
I've gotten last month's bill waived, but still received a passive-aggressive email with bad English by a Territory Account Sales person from my region about how my account could be suspended, if I didn't reply to the email within the day. I'm not sure I would trust said person to handle my accounts, even if I was on a corporate budget.
I'm still in the process of moving most of my workload away from AWS.
All these stories of providers giving "good will" credit for these massive charges really concerns me when you look at how other parts of these companies ignore their customers or only reply with scripted responses.
At their revenue, don't care about 5K charge, they can send to collections / sell to 3rd party collections agencies.
They do care about keeping you happy as a customer since your employers will be swayed by their employees.
So the former is much more likely to succeed, the latter will just make you look like a scammer.
At larger sums - they will do much more rigorous checks to avoid issues.