It seems I can organize 26.7TB (two servers, 6TB and 21TB) of space with 25TB of monthly outgoing bandwidth. To meet bandwidth constraints, a max average of 100mbps (for downloads, uploads up to 2gbps). That depends on what people actually use, so gigabit speeds for downloads can be expected if it's not a very big file. Of course, this depends on the downloader's actual down speed.
I got most of what I wanted, able to use PayPal to pay my server bill making it pretty easy to start when I want to. Prices will be exactly as listed above.
The project's a go, but it's a while before I work on it because I must finish the Blockland part of this first.