$1500/month for Equinix + Bandwidth? We got quotes from them before and rack was low, but I wasn't finding super cheap bandwidth like that. Did you go with Cogent or similar?
I just looked what 250TB would cost us on s3, $20k/month, or $240k/year. ( im not even counting the put/get usage )
You can build it, for ease of math, 100x 3TB seagate constellation. 100x $250 = $25k, another $5k easily covers a 45 jbod and raid card and server with ssd zil and arc for zfs and you're done. so $30k. Get 2 more for redundancy and backup as you see fit.
So over 3 years, 720k vs apples to apples 90k ( if you got 3 of those servers) so you save say $600k. You can get a decent remote dev for $200k/year for that time.
won't be redundant power or connectivity though - but it's not cost prohibitive - just double the price.
people - this is what amazon makes their margins on. doing this work for you, so you can click a button in your underwear. if it makes sense for you, it makes sense - but if it doesn't - it doesn't.