I saw people burning through cash in the cloud, which makes you wonder weather money is any concern at all.
A full-time system administrator costs more than 72k a year.
I've seen enough buddies spending enormous amounts of time doing AWS devops on top of paying the AWS premium when they could have gotten away easily with a less than a handful of VPS (+ optionally $100/month worth of cloudflare as a CDN).
If the person is already on payroll doing a number of other duties, the time/effort to set up such an environment as described in the post could be as short as a couple of days work.
In most cases cloud computing is actually still a very cost effective solution to infrastructure. But with infinite scalability also comes responsibility.
In the case of the OP, had they had their own hardware they would have noticed that had written bad code (it would have crashed or become very slow at least), but the cloud just scaled up and processed their code.
I'm not trying to defend Google in this case. Billing 72k when a 100 USD limit is set sounds like a scam.
Also, companies that employ bunch of developers can find a developer that has IT administration expertise and allocate some of his time to this. Still cheaper than 72k a year or employing someone full-time, if IT requirements don't call for full time job.
It's not just cloud vs full-time.
Someone who makes 35k a year costs much more. Think about office space, training, insurance, payroll costs etc.
You only really start saving at some scale (get a small core of cloud-literate admins, and now you can have them run thousands of systems for effectively no incremental cost)
And the way these cloud services go, the 72k was only detected because it was an one-off event. Turn that into a base-level inefficiency that costs that over a year and what have you then.
Of course self-hosting on real hardware is not quite as simple or cheap as GP made it out to be. But everything in your post can be solved with simple fixed pricing, which is still the main point: there are no dangers of wildly variable pricing or accidental massive bills as there are with cloud hosting providers.
If you need a number or xen or kvm VMs with a lot of RAM assigned to each one for testing something, you can fairly easily set up an older Dell R910 (quad-socket system) with 512GB of RAM for under $2000.