Is it possible to actually achieve PR 6 - 8 without spending thousands of dollars? I've come as far as to PR 4, but it always stops there, and won't increase even though I continue building. What's the best (easiest) way to achieve such high pagerank? (Yes, I know, pagerank isn't very important, but I'm still asking).
Of course it is possible. You just need to have a great site that authority sites will naturally link to. If you are talking about some run of the mill site that doesn't offer anything very unique, then it would be difficult to do without buying links.
i just gave some quick seo advise to stephen fry, check his site. its got PR6 and not even well optimised. content is king here though.
from PR4 to the next one is a big step and you will need LOT more backlinks to get there. it helps if you have organic links otherwise yu will struggle. quality site with helpful resouurce will get you some organic good quality links
more backlinks from high PR is the key. If you dont have the unique content to gain natural backlinks, you will have to pay to get some.
You need more optimizations, Try to increase quality backlinks, submit to social network sites as you can, direstory submission etc. I guess you don't need spend much.