They use Edgecast's CDN (which is now owned by Verizon?)
https://www.edgecast.com/company/news/edgecast-powers-imgur
Off the top of my head, I think they offer their bigger clients pricing of $0.02-0.04 per gigabyte. I could be wrong though.
44040192gb *0.02 = $880,803 / 12 = $73,400/month.