I think get no way to get quality backlinks without much efforts. Like lifeplayer's say, the only way is pay for it.
I think any website higher PR then yours, link which is pointing to your website is quality links. By many ways like social bookmarking, article directory , commenting to blog post, edu website.
Quality backlinks come from high ranking sites that RELATE to your keyword or niche. Creating too many backlinks on irrelevant sites won't count as much and won't be considered quality backlinks in Google's eyes.
It is a mistake to use PR as a measure of quality. As a general rule you don't get links from sites with a high PR. And those that are trying to get you to buy the filthy stuff are the worst of the worst. So scratch it off the list. You do however want, do follow links, that are going to last, that are going to remain do follow, which come with anchor text and which preferably point to your internal pages. It's not rocket science this. Just a measure of common sense.
PR is not something that should guide any SEO practitioner. I've seen ranking for one of my own site boosted past sites with substancially higher PR, and these links have been coming from blog with low PR but very high relevancy. So I wouldn't stare too blinding on PR in search of quality backlinks. PR is not a measure of quality as much as the backlinks and relevany your potential link partner has.
You haven't really answered the question. What is a quality link? Any old link that gets approved? Is that all there is to it? I understand the point you are making about a submission services that only charges for submissions that are approved but that hardly constitutes a quality link. What in your mind is a quality link? Most of the sites they list have been set up for the sole purpose of selling approved links. Is this not a risky investment given the fact that Google has already taken steps to devalue the practise?
Again a bit dodgy. Buying high PR links can get your site trashed. Sites selling PR should be avoided. They are a ticking time bomb.
Main thing is on page seo to build unique quality content. Then you can focus on meta tags and title page. Next is off page seo. You can find forums and blogs related to your niche if possiable and make sure they are do follow which most now a days are. Next create a facebook fan page while it is no follow it has high potential for traffic. You can like other sites relate to yours and thus should get a lot of traffic and may improve in rankings.