There is no set value, sometimes you get a cent per click and sometimes you get more than a dollar. It all depends on the type of ads being shown on ur sites.
There's really no fixed price per click. Price varies from very low to very high $ Some people claims to have earned more than $20 for a single click and some people complains for getting just around 1 cent per click.
as all the guys said above it depends on CTR, advertiser bidding, just one more thing they didn't mention is your pages quality, google some how recognizes your pages quality and depending on this aspect the percentage they share with your increase or decrease. for me i get from 0.03 to 0.4 dollars per click
Depends on the phase of the moon, seriously I've had one ad worth x and later in the day the same ad might give me 4x or 1/2x.