It's not the hardware costs, it's the head count to setup and keep those database instances running, backed up, and tuned. That's the IaaS pitch -- no sysadmin.
As for the vendor lock, most of the datastore API is very similar to other nosql APIs I've seen. It wouldn't be trivial to switch, but not impossible either. I imagine it'd be even easier if you used a orm that is widely supported but I stay away from those, so I couldn't say for sure.
In theory I agree with you, but the reality is that even though SQL databases are all on the same "standard" there is enough non-standard things that it in practice becomes impossible for high performance apps.
I'm afraid I don't see your point. Docker, and some of the other new system tools seem like great products. I'm sure they make sysadmin's lives easier than when they had to run everything via custom shell scripts. It probably makes them more efficient, so you don't need as many sysadmins per server. But I don't see how it is ever going to reduce the need to less than 1.0 sysadmins. And just as it will make sysadmins that work for your company more efficient, so to will it make IaaS/PaaS' sysadmins more efficient.
As a developer, I have very little interest in administering databases, servers, networks, and so on. It's not what I'm good at, and it's not what I'm interested in, it's not what I know. That the tools now use Turing complete configuration language that also happen to be a fairly popular general purpose languages doesn't change any of that.
Certainly, the IaaS/PasS pitch isn't for everyone. But for those who are in the sweet spot, it is a very compelling pitch. Frankly whether or not the platform is open source doesn't really impact its appeal very much. At least from where I sit.
As for the vendor lock, most of the datastore API is very similar to other nosql APIs I've seen. It wouldn't be trivial to switch, but not impossible either. I imagine it'd be even easier if you used a orm that is widely supported but I stay away from those, so I couldn't say for sure.