It might be cheaper but still not free. Cost of electricity + time to maintain + Raspberry Pi itself. Not to mention that you don't get the variety of servers (for geo-location or more diverse networks not tracked to you by websites themselves).

Well the Raspberry Pi is already on 24/7 running a few other services for my home network. But even then, the energy consumption per month costs pennies. I update the device once a quarter and it takes me 5 minutes. These costs are so negligible as to have no impact on my decision making process.

Not sure what services you’ve looked at, but it definitely doesn’t cost $10/month.

Your personal solution seems pretty good though.

Why would you? Nobody can connect to it without your private key. Or is there something I am not aware of? Genuine question, as I am running wireguard in a few places and thought it was secure by default.

WireGuard is pretty minimalist and has great defaults, AFAIK if you manage to set it up you're good.

Unless your credentials leak, of course, but a security expert would have that same risk.

You do not need to be a "network security expert" to safely run a WireGuard server