I noticed that most people only sell 3-10 links for their high PR page. I just don't understand why don't they sell 20, 50 or 100 links for their page? Is doing so get you banned from search engines?
You should really read the Google Webmaster Guidelines: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35769
I'm not too sure, but I do know that the value of links (the google juice) goes down if there are tones and tones of outbound links on your webpage. So maybe they just don't sell more because there isn't a demand for more.
Put yourself in the buyers position. If you are trying to get some decent traffic from this new link that you bought you don't want your link to be placed next to hundreds of other people's links.
if you have 100 links on one site, then your site will look like a link farm and will be penalized by google. also, people whom you sell links to will not get any benefit form the links. the way PR juice is passed is by deviding the page PR between the number of outgoing links on the site. for example, if you have a site with PR6 and have 5 outgoing links, then those 5 sites will devide the PR6 betwwen them and get a boost in their page rank (your site PR will not go down). but if you sell 100 links, then that PR6 will be devided into 100 sites meaning no real benefit. most people buy links know this for which they will not buy any links from a site which has more than 10 links or so. another important thing to remember, if you buy or sell links, do it with relevant site only. if a recipe site has link to real estate, casino, online dating etc, it may be identified by google as selling links because there is no reason for a recipe site to link to a casino site as a related resource
sultanofseo had it right. 100's of outbound links on a page may look a bit spammy, especially if the links are in unrelated niches. Such a page would look whored out and nobody would buy links there. Anyway, PR would be so dilluted it would not be worthwhile to link buyers.
Just a piece of advice, sell just a limited number of links per page, if you want to make more money then also offer blog posts on your site which can make you money money. It is better to make more pages then just to make one and sell hundreds of links on that page.
I know the more links you add to a page the easier your site would be flagged as spam site and deindexed. It is true what said above, Google dislike sites negotiating with links.
As Google doesn't allow link selling, too many paid links on one page will easily let Google know this violation.
Google Webmaster says don't sell links. I wish someone had told me that years ago. My site went from PR7 to P$3 when I started selling and buying links.
I haven't seen it that much in English but one of the most visited sites in the Netherlands is http://startpagina.nl/ it's got a lot of copies in the same form here but basicly all it is a bunch of links nicly categoriced. Buying links is not that visable but it's the way it works as when you want to get listed on them you realy have to have a great site or are willing to pay. This site gets on it's frontpage alone 4 million visitors. Each subdomain and frontpage consist of 150+ links and basicly zero content. When you take the G rules and apply it on these kind of sites it should mark spam all over it but that's not what's happening...so i think it's not just a simple rule of having to many links is a spam site and pr is washed away or decreased...it's more complex then just that
it waters down the value of the inbound link if it comes from a page with many(SEO) and it lowers the chance the of getting traffic if the viewer has 100+ to choose from.
Too much link selling will get the website banned by google or the PR of that site will dratically decrease as the site will have too much outgoing links