It all depends on how much the advertiser is willing to pay for that one click. Hell, I'm sure Google would be happy to let them pay $1,000,000/click. There's no limit.
it depends on the keyword and cpc for that keyword. tell us the keyword you are talking about and you will get more answers.
its hard to say. depends on how much advertisers would like to pay for the clicks. entirely depends on the niche
Lots of people I've seen in this forum today have been getting like $20+ per click, which is about as high as I have seen.
It depends on the niche and the advertiser. Nothing is fixed and there are no limits as far as I know.
The limit is 5 cents per click. Anything more and you will be banned by Google within 72 hours. Just joking. There is no limit. The limit is set by advertisers' willingness to bid high PPC prices. Of course, we only get a portion of what the advertiser pays. Google doens't tell what that portion is.