There are tons of High PR backlins available on services like Linksmanagement, but there are also links that are way overpriced and some that could even hurt your site. Buying or renting high PR backlinks is still considered black hat, but so is almost every form of link building. With Linksmanagement I at least have the opportunity to cancel an order or have the link removed quickly and easily.
Finding the hidden gems in the large database of available domains to get links from is a daunting task but my technique for checking the pages for TF, is a good indicator of the power of the site you are going to buy links on.
You can go further into checking the domains your going to buy cheap backlinks from with ahrefs, moz, or looking further into majestic. Another thing that is sometimes worth looking at is the traffic which you can check on sites like spyfu, or semrush. Seeing things like where the site is actually ranking can be a great indicator of the quality of the link as well.