The central problem with the idea of "buying" traffic is that if people are only visiting because of a financial incentive, they're very unlikely to be interested in your site. And if you're selling traffic, then the incentive is to make the numbers as high as possible.
You can "buy" traffic from PPC - Adwords and similar which is genuine, but if you're looking at a "pay $100 for 10,000 visitors" sort of a deal, it's very unlikely to be worth your while.
Do not buy traffic. Build a product (eg website) around the needs of people - if you fail to do so, no meter or indicator of success (traffic, hits, etc.) will actually lead to sustainable business and/or conversions. I mean you might end up with high traffic on paper or in the stats program of your choice, but it won't get you anywhere.
Buying traffic is not the best t promote websites. If your website is getting natural visitors then it will be the best for your business, So always try to generate back links on high PR websites with the help of Off page SEO techniques like forum posting, article submission, profile submission, social bookmarking and guest posting.