Regarding Adsense and payouts , does it matter which ads appear if either way they are clicked, or do some pay

I am trying to figure this out w/ Adsense. Does it matter if an advertiser pays more for ads on my site or does it simply matter how many times ads are clicked? So if a site gets 250 clicks out of 3,000 impressions, will it get more money if the ads cost more to the advertiser or is it based simply on the ration of clicks to impressions?