Add $20/month for electricity: 3 years: $197/month 4 years: $156/month
Could that rent respectable enough device(s) in the cloud?
Granted I didn't do this math before I dropped a few stacks on hardware. I really wanted to build it, configure it, play with it, etc. It's been a really fun project for me, and I've got a bunch of other stuff I want to do with it in the next few years (10GbE, X11 nodes, set up dedupe, etc).
So he's currently using about 10TB of 60TB of usable space. If he uses Amazon S3's standard storage, he would be paying about $230/mo. If he uses infrequent storage that is $125/mo. That goes up as his usage goes, so when he's using 30TB that will be $690/mo and $375/mo respectively. He also has the benefit of high speed ethernet with the home NAS, unless he has fiber 1Gig internet, in which case speed is probably a wash. I'm not sure if there are other significantly cheaper cloud storage solutions at that scale.
So I'd say he hasn't done too badly for himself, though he probably could have saved some on the hardware by getting cheaper parts.
Other way around; he's using ~50TB of ~60TB with ~10TB free.
Amazon cloud drive is unlimited and 60$ a year.