Thats a good price, belt tensioners are extremely difficult to get. 2 years ago i had a friend that works at the chevy dealer do a nationwide search, zero,nada, nothing in entire country. Finally found used one from a vender,cost me two hundred.
Monster you are lucky, it took me two months to find mine and it was used as i said. There are some new billit ones the guys on here got together and made some kind of deal to get them made, i think they are also still available, do a search for billit belt tensioner if a new one is a must.