Tunneling isn't that big of a toll on resource, it doesn't require storage/disk space nor compute power (CPU chips), all it needs is ingress/egress (spare bandwidth). A non-profit or decent business in telco can easily offer it, consider that many hosting companies offer entire package in free tier today (compute + disk + egress).
For several years, ngrok was practically free, only recently they've started monetizing once it gained popularity.
For several years, ngrok was practically free, only recently they've started monetizing once it gained popularity.