Basically the advertisers decide how much they are willing to pay per click, and google decide how much is their cut, and publishers recieve what is left.
totally depends. i got site that pays 30 cents or more per click, and another site pays 1 cent a click. depends on your niche and where your visitor is coming from.
each click has its own weight, some are worth $0.03, where some can be $2.59 I saw some where on google adsense, that google pay %65 to us, that is, if a click worth $1, then google gets $0.35, and we get $0.65