As I understand from your question, there are two things here one is average cost-per-click which is how much you actually pay for each click and this is usually lower than how much you bid (max CPC). I've seen avg. CPCs fall by 10 - 50% (depending on the industry) when Quality Score changed from 5 to 7 for keywords. You can actually track Quality Score and overlay it with avg. CPC and other stats to see a correlation for your account. We created a tool for doing this. The second is Google's suggested cost per click which is the recommended first page bid that Google shows next to each keyword. This is a function of your Quality Score and competition. You'll notice that keywords with a low Quality Score have a relatively high required first page bid. Please feel free to email me (geetanjali att optmyzr.com) with any questions!