PageRank (PR) is a measure of how many Page-Ranking sites link back to your site; in addition the age of the site is relevant. The range is from PR0 to PR10, where a PR0 site has no ranking and a PR10 site might include Facebook or Joomla’s main site.
The correlation between age/backlink relevance is only known to Google and is an algorithm that is not published anywhere. Exactly how many links are needed and from whom is not known, so you can’t say you should have a PR1 or PR2 or more now simply because your site is aged and has a lot of backlinks.
The relationship between you and domains linked to you is important however.
If you had even just a few relevant sites linking to yours with top PR’s of 10, your PR would improve quickly. If you have 250, irrelevant links or from low PR sites, you may get a PR of 2 or 3 – maybe… The chart below is thought to be fairly accurate representation of what the effect of different amounts of incoming links and how they improve your PageRank.
|PR||Links For PR3||Links For PR4||Links For PR5||Links For PR6||Links For PR7||Links For PR8|
Buying links is generally not a great idea but some relevant high PR links are worthwhile SEO. The key is in relevance. An incoming link from a high PR site not related to your industry (unless they are PR6 or higher) is not going to help much and could be penalized even.
If you need SEO help contact me today and I can check out your SEO and see if you are getting what you are paying for elsewhere!