If you think 250TB of backup is a lot, then you don't need tape.
I currently backup about 1PB and data storage is growing exponentially here (gene sequencing data). Tape is the only cost effective solution for us.
I do agree though that tapedrives are ridiculously expensive but it's a sellers market. Tapedrives don't sell in massive quantities so the price stays up, mainly because there just aren't that many suppliers.
On the other hand. I called a shop a while ago to see what they'd give for our 5x LTO4 tapedrives since we upgraded to LTO6 and they only offered us 30 euros per drive. So if you don't need the latest drive out there, you can save a lot of money by buying second-hand.