if u have high pr then search engiune crawl your site asap. and your page in your site will be index soon. so if u have high pr then you will be get benifit from search engine traffic. (its help in serp)
To put it simply, you need backlinks! I would suggest focusing on ones that are dofollow if you are concerned about PR,
Well none Actually the value of the site increases to about $300 per PR5 domain... It depends. Focus on getting traffic better.