Smart pricing is when Google sees your traffic isn't converting so sort of puts this crap "cap" on your CPC. Earnings overall go down--it isn't just for one site... even if it's one site out of a hundred causing the problem. Avoid it by NOT trying to trick people into clicking your ads. This will result in a low conversion rate on your account and thus put you at risk of getting smart priced. How to recover? If you have more than one site remove ads off different sites for 1-2 weeks and see if the CPM increases.