i was pushing 100 T / month with one server 1Gbit unmetered at 250$ / mo , also music site.
Also, most of our cost was for the hardware(not the bandwidth). We went with top-notch storage with RAID and a bunch of ram. In hindsight, we should have bought the hardware for one-time fee but didn't for cash flow reasons.
FWIW, 100TB (approx 300Mbps continuous) costs us approximately $450/mo with a good quality host (Quadranet) with a good blend of upstreams. A cheaper host (Ubiquity) charge us about half of that. It's worth paying the extra for sure.