Well, except if something's gone wrong and my bills are suddenly shooting up, that's exactly the kind of time when some piece of software might misbehave, and fail to freeze everything. And it's not really very easy to test either.
This seems like the kind of thing you really want to get right, and it will be (I imagine) hard to get right. If it was easy, I would expect some company to offer it (along with, of course, a guarantee that if they mess it up, they will pay my bill).
Sure - and if you need that, buy that. WHM/Cpanel and Plesk both let you have 100% guaranteed monthly costs with vendor configurable response to over-use of resources. You can get that for $5/month or less - just not from Amazon, because that's not what they sell.
Nobody rings up Caterpillar and complains about the costs of leasing/running/maintaining a D9 'dozer if they're doing jobs that only need a shovel and a wheelbarrow.
Tools for the job. AWS might not be the tool you need. Or might not be the tool you need _yet_.
I've been involved in renting heavy equipment, and it doesn't work like Amazon. No one gets unexpected massive bills, you agree before what the bill will be. I don't see the comparison you are trying to make.
If you leave it parked in a pit overnight that fills with water, you may find yourself on the hook for a big bill if your insurance finds you negligent. Likewise, if you neglect to perform required maintenance, you could find yourself on the hook for an expensive engine overhaul.
Even heavy equipment rentals can result in large unexpected bills if you don't pay attention to what you're doing.
There's nothing "unexpected" or "unagreed beforehand" about Amazon's pricing or costs either. You order a medium EC2 instance and we all know exactly what the bill per hour will be.
There's nothing unexpected or un agreed beforehand about the ordering/provisioning process. You ask AWS to start one, they'll start one. You tell them to stop it, they'll stop it. You get charged the known agreed upon rate for the hours you run it. You ask for 10, you get 10. There's even checks in place - the first time you ask for 50, you hit a limit which you need to speak to them to get raised before you can get a larger than previously seem bill.
Same with your earthmoving gear. You ring up for prices and they'll say "$200/day for a bobcat, $2500/day for a D9 - includes free delivery in The Bay Area!"
If you need one bobcat for one day at 10 Infinite Loop, Cupertino - and click their web order form and say you want 10 D9s for one day at 1 Infinite Loop, Cupertino (and happily click thru all the never-read the web interface confirmations) - you should 100% expect to get a bill for $25k, as well as dealing with clearing up after parking 10 'dozers in Apple's parking lot.
This is not "unexpected". From the vendor's perspective $25k is not "massive". You knew and agreed to the prices and had every opportunity to calculate what your bill was going to be.
If you were only expecting a $200 bill - that's kinda on you. The earthmoving guy has heaps of other customers who spend many times that every single week - and they all started out as some guy who ordered a $200 bobcat or $25k's work of D9's as a one off. You are just another sale and another prospect in the top of the MRR funnel for him.
(Note: See holidayhole.com for a contemporary example of an unbounded earthmoving bill! ;-) )
This seems like the kind of thing you really want to get right, and it will be (I imagine) hard to get right. If it was easy, I would expect some company to offer it (along with, of course, a guarantee that if they mess it up, they will pay my bill).