i recommend lowendtalk what fly.io doing is running colocated baremetal servers and using firecracker to overcommit (probably via memory ballooning and other disk compression on demand)
if you are going to haggle over $2/month then you are better off just connecting your raspberry pi with wireguard/cloudflare tunnel on a residential connection
if you are going to haggle over $2/month then you are better off just connecting your raspberry pi with wireguard/cloudflare tunnel on a residential connection