Just a hair under $5 a month, but unless you have a reason to deal with AWS complexity, you're probably better off with something like Digitalocean or Vultr for the same price and less surprises.
Which you can also do at Digital Ocean (note: you have to take a snapshot, and destroy the droplet in order to suspend billing).
While it might be pennies (or less!) - I'm still wary of how Amazon bills everything separately - your data at rest, your CPU, your bandwidth. I don't know if Digital Ocean would be any cheaper - but it sure strikes me as being a lot easier to predict. Maybe I'm just unreasonably afraid of what I perceive as "billing complexity" at Amazon.
Now I'm actually tempted to set up a small classroom using skolelinux/DebianEdu[1] on Digital Ocean built around a central droplet running the servers - and seeing how easy it is to suspend every thing to a dormant state and revive it... mostly just to play with the ldap-stuff.
It's also only 512MB of RAM. For a dev box, m4.large spot instances work really well price-wise too, especially if you stop them when you're not working.
EC2's t2.nano, at 0.6 cents per hour, is incredibly close to free. (And that's not even counting the 12 month 'free tier'.)