Is Quality Score a gimmick by Google to make money?

Somewhere in the mid of 2005 as a revolution towards stressing on the fact of relevancy, Google came up with the concept of Quality Score. As per Google below are some of the factors that influence QS:

• Historical clickthrough rate (CTR) of the keyword.
• Your account history, which is measured by the CTR of all the ads and keywords in your account.
• Relevance of the keyword to the ads in its ad group.
• Relevance of the keyword to ad and to the search query.
• Your account's performance in the geographical region where the ad will be shown.
• Other relevance factors.

Since then Google has added lots of factors that would influence Quality Score, such as the inclusion of landing page quality and landing page load time and so on not to forget ‘other relevance factors’. Above all one question that hunts all SEM professionals is how is Quality Score Calculated? What are those ‘other relevancy factors’?

To all readers I would like to share the result of a test conducted across multiple accounts regarding QS. For a test period of 15 days bids were reduced drastically for all keywords with low QS (1 to 4), leading to which keywords that were consuming almost 60% of total cost of the account dropped to just 18% of the total cost contribution impression and clicks from keywords with low QS dropped by almost 80%. CTR for all these keywords went from bad to worst during this period. (Point to note: apart from bid changes no other changes such as ‘Ad Copy changes’, ‘Landing Page changes’ were done to the account). Strangely by the end of the test period QS of almost 55% of keywords with low QS (1 to 4) in the account had gone up to (6 to 7). This sudden change in Quality Score trigger’s certain question in my mind.

• What made Google to suddenly change the keywords QS to that high?
• Did Google suddenly realize that Keywords and Ads were very relevant in that ad group and it has assigned low QS and raised the QS?
• Did the past 15 days CTR (worst ever in the history of that account) match to the industry standards and hence raised the Quality Score? Finally important one
• Quality Score for these keywords were increased just because Google stopped making money on these keywords? If yes then the whole concept of Quality Score from Google is just a gimmick to make more money?

If anyone has an answer to these questions, your comments are welcomed!