Dynamic, paid links...good or bad?

I run a very large 6 year old niche site with around 137,000 pages in Google. About a year ago, I sold space for a few links at the bottom of all my site pages for $150 a month. These links are generated server-side, then included as normal anchor tags in a small font at the very bottom of my pages. These links are completely unrelated to the topic of my site and are different on every page load. How severe of an impact can this have on my site's ranking in the top search engines? For such an established, highly targeted, and information-rich site, it does appear surprisingly low in most results...

I would try to sell links related links to your site.

if G sees you have links to baking sites, and your site is a webmaster site, they my look down on this.

Actually, there is less benefit to the buyer, than harm to your site.