My current little side project uses about 200-300 MB of database storage. Using Heroku, that would cost (pr month) $9 on their shared postgres database, $10-15 using mongodb, $50 using heroku's dedicated production postgres service, or $125 using redis.
I stand corrected. I was using the prices from redis-to-go, which was the only available option last time I checked, and the service with the big prominent link at the top of the heroku pricing page. Good to see that there is some competition in the area and that prices have come down a bit. Still not cheap enough to move my hobby project from a 1GB VPS, but reasonable enough if I ever turn my project into something that might make money.
That's quite a difference.