If you are interested in Terraform modules and have an interest in running a Syncthing Relay Server you might find this helpful.
Also published as an actual Terraform module so you can simply do the following:-
module "strelaysrv-node" {
source = "ndejong/strelaysrv-node/digitalocean"
region = "sfo2"
hostname = "node0-sfo2-digitalocean"
user = "<username>"
user_sshkey = "<ssh-public-key>"
}
Digital Ocean is targeted here because their per/TB cost is better than most of the alternatives ($5 per 1 TB per month at low end) if you require more TB, simply deploy more instances.