Not the OP, but the reason I've looked at co-loing my own server is to host off-site backups in the 400-2000TB range. With the right colo price, it can easily be 1-2 orders of magnitude cheaper than cloud storage over a 5-year timeframe.
That sounds about right. My back-of-the-envelope is $2000/mo to colo (not including up-front hardware cost) and $12,000/mo for 2000TB from rsync.net (although you might be able to get a bulk discount).
Costs. We actually did this for EU - looking to replicate same for the US.