from what I have seen (I provide VPS, not VPN, but some of my customers buy the VPS just so they can set up a VPN) what you are really providing is US internet.

Bandwidth, cpu, etc... is all but free. your big costs would be handling the abuse desk.

Now, depending on how efficiently you handle the abuse desk, your margins could be pretty good.

On the other hand, your fee per user would have to be pretty low. The people who live in countries with restrictive firewalls tend to be /really/ cheap. but, if you can keep your abuse costs down, the cost of servicing a particular user is almost zero.