You can easily find that there still be sellers who post thousands of back links for sale when you visit any popular forum. The truth is that the numbers game doesn't work anymore. Nowadays, it's more about quality than quantity.
Most webmasters and internet marketers look at search results of their competing keywords then turn to check out the back links. They're confused because the site may only have a few hundred links pointing to it compared to their own sites which have thousands of back links. But if they looked closely, they would realize that the number one site has back links from more relevant or more trusted authority sites.
Back links are crucial in the SEO. You can either go for a large volume of links or go for trusted links. If you choose the first one, you will always be out there in the webmaster forums hunting for even more and more links. The problem is that you will meet some unscrupulous dealers who try to sell you links from non-trusted or artificial link farms in the hunt for those back links. Don’t be so stupid to deal with them because that just likes suicide. At the same time, your competitor has acquired maybe two or three more votes from other quality sites to get or keep its status as the number one site for your similar keyword.
It's a never ending trap that often so many webmasters and internet marketers seem to fall into and never get out of. So if you really want to make success in the real SEO game, think "quality" not "quantity".