Quality Score has absolutely nothing to do with your bid. QS is about 65% click rate, 25% relevancy and 10% other factors. Relevancy is about your keyword themes matching the theme of your page. If the theme of your page is about dog food, any keyword not related to that theme will take a 25% hit in QS. In fact, it may be even lower because presumably your ad would be about dog food and nobody is going to click on it if they searched for something totally different. You can learn more by reading my free Adwords FAQ.
As much as you improve your QS your bidding price will be lower, write relevant ad, add relevant keywords, add negative keywords, and optimize your landing page with proper keywords.
Yup, and dont panic if it does not improve instantly. Though QS is calculated each time your keywords trigger your ad, they show you a rough estimate which updates once in a while (Same like how Page Rank works,but in a faster manner) Your historical CTR ,Account history, Landing page quality, KW relevance and lot more complex (Not so complex) stuff works together to give you a QS.. The better it is, the less you pay. Simple!
Quality score depend on landing page and cpc depend on quality score. but quality score does not depend on cpc.