I think you can do a lot on the free tier, my son only recently started spending a little to unlock some of the upgrades.

Personally I'd rather see subscriptions fund a server that's always up. I've researched running my own Minecraft server for the local kids, but it's really not worth it.

That's a strange sentiment to hear, and somewhat disheartening. Minecraft servers are easy to set up, and can easily run in the background of an old server or PC.

I've been running one for over a year on my gaming PC and home internet connection.

I'm running a vanilla minecraft server for 4-6 people on the Raspberry Pi 3 and it runs beautifully, never had any problems. Pi2 was a bit slow at times, but the latest Pi3 has enough horsepower to support that many people without a problem. So really, setting up a minecraft server costs $30 for the Pi + $10 for the sd card. At 5W power usage it can stay on all the time.

You can do okay on a DO VPN for say $20/month. I did this for a while but it was only me and a few friends, and when we wanted to use a modpack I moved the server an oldish computer in my house as it needed more grunt.

Calculating the power costs put it at about $30/month in electricity, ignoring all the time wasted getting it running.

If your data isn't in a free format that you can open and work with on your own then you don't own it.

Being a free format helps. But it isn't necessary. The main thing is that you can access the data reliably even if the original software or servers disappear (may require you to make your own periodic backups).

ROBLOX has Builder's Club which is subscription, but you can also just buy some ROBUX from time to time if you don't want to subscribe. It is pretty playable with very little spend, most games on the platform aren't play to win (because the players themselves make the games).