The same thing - doing almost nothing when a VPN endpoint - applies to other VPSes at half or less the cost, e.g. http://www.lowendbox.com/blog/forever-hosting-19-95year-256m... - 20 USD/year. Now these are smaller instances, likely more contended, but that's precisely the point - when you don't need much, there's not much value in over-provisioning.
Anyhow, I've said my piece; I think EC2 is over-priced for this specific task; there are other options; and (at least in my case) they aren't blocked by SO, owing to not being as mainstream.
Anyhow, I've said my piece; I think EC2 is over-priced for this specific task; there are other options; and (at least in my case) they aren't blocked by SO, owing to not being as mainstream.