We all know buying backlinks is black hat seo. The price quoted for that many backlinks appears to be unbelievably low. Too good to be true some would say. You should investigate fully before paying any money.
I can tell you from my own experience. One of my sites has a lot of backlinks and still has lower page rank and lower SERP then the other with only 2 backlinks.
More is not always better. Backlinks from sites with PR 0 or 1 will not help you.
Go after sites with at least PR3 or higher.