If you were intending on buying a high PR link just for the sake of one Google update to inflate your site's PageRank, I'd say "save your money". Unless you're intending to keep paying for the link (which is advertising) there really is no point. However, I will offer a different perspective in that I bought a bunch of TLA's because I liked the blogs I advertised on and wanted to reward the webmasters by figuring them into my advertising budget. I bought links on sites directly related to my sites in content and a suprising thing happened: 9 out of 10 of the sites I advertised on wrote a blog post about my site(s) and I got added to a few blogrolls, so I blogged back and a natural linking relationship was established. I will still figure those particular bloggers into my "budget" and I've also developed some other "friends" through the reciprocal posting etc... So, if you see what I'm saying: just buying a link for PR is useless, but buying an advertisment on sites you like can be an "icebreaker" and get you some new found friends which is what will really build up your PR in the long run.
I would imagine its too late for this PR update , but im sure the next time indexed will benefit you! Be careful about telling webmasters here that you are purchasing a link.. Google can penalize you now if a webmaster points your site out to them!
Well thank you for all of the advice. I've decided that buying one just for PR is not a good idea. I will try to exchange links with similar content sites and hope that this will help my sites PR and also bring in more traffic.
If you have a goal to influence the new toolbar PR, then to buy the strong links is late. I experimented with the site having PR 1, and put several links from websites with PR5 and tens from PR3-4 , the update had place in two weeks, however, nothing has changed, PR remained 1.