Unfortunately, cheap and quality don't really go hand-in-hand when it comes to links. When I've needed links in a pinch and had a budget to work with, I've gone to these guys:
Code:
http://www.text-link-ads.com/
If you tell them you run a small SEO firm and want to become a reseller, you'll get a significant discount in the form of a "commission." The size is generally dictated by how much money you spend, but definitely talk with your account manager about that. If you're nice, you can also get them to do most of the hard work for you. They'll send you an Excel spreadsheet with a few hundred links listed by PR and a few other qualities. You select the ones you want and generally they are live within a few hours. Make sure you know specifically what keywords you want to target.
Good luck.
EDIT: Sorry, didn't see you needed to pay with PayPal. I don't
believe that TLA accept PayPal, but you could always ask.
If you don't mind me asking, what is your budget?