The idea behind using multiple factors for scoring the ability of a specific keyword to send a qualified lead to a product information page is to make a level playing field.. in terms of visitor satisfaction & purchasing satisfaction of the person buying the keywords.

Knowing the major factors helps tremendously in using words which the automated system believes are accurate. One of these is ensuring that the keywords you bid on are also used in the ad text.

Google AdWords Quality Score Factors Demystified » eWhisper.net

That will help with minimum bid prices. Also, Google builds a history on your account, and past performance also matters.

As for ad position: "According to Google, the things taken into account for position are Max CPC, CTR, Keyword to Ad copy relevance, & Keyword to Search relevance. When you're talking minimum CPC: it's CTR, Keyword to Landing Page, and Keyword to Ad. I think weighted in that order."

Understanding Factors for Google AdWords Placement and Quality Score

10 Ways To Increase Adwords Quality Score

In many cases for valuable keywords, competitors will raise costs by bidding more.

Kevin