Out of curiosity, how do you actually determine the amount per click for each and every specific ads? There are obviously a lot of variables here.
You can't calculate the specific price of one advertisement. You can only see what you are getting in general. Less ads means less clicks and less clicks means less money. That's the point.
Lesser number of ads means higher EPC because you are eliminating exit points for your visitors which pay low. If I have a forex site and my adsense advertisers are forex service providers, I would want my visitors to click the ad which pays the most. By eliminating low paying ads (by limiting the number of ads per page), I'm forcing my visitors who are interested in forex services to go to the website of one of the high paying advertisers. Having tested adsense for over 3 years on several sites, I'm convinced that lower the number of ads, higher the earnings.