I'm aware of one similar company that used to fit sixty $20/mo VPS in 1U. They were working on a couple hundred in 2 or 3U when I left (harder than you'd think), but they also have a cheaper tier now because of competitors pushing VPS down. Margins on VPS, even without oversubscribing RAM, are pretty decent once you get past the capital but they are decreasing in a race to the bottom just like shared hosting before it.