My cyberghost vpn is under 3$/mo and has unlimited usage. It's hard to imagine any pay-as-you-go scheme coming even close from a cost perspective.
Managing your own server at 5$/month does not make sense from any perspective other than “privacy” if you believe that.
I use a router behind my router at home that runs 100% of my traffic over a VPN before it leaves the building. Any services that don't work, I simply don't use them. Someone else will take my money.
I'm on a $10/year VPS with 100 Gb/month traffic. Not great, but not terrible.
Not in my experience. Using it now on a super budget VPS ($4/year), very little CPU/memory usage even when streaming video.