I agree in principle, but this fraction would be easy to get if they just had to buy a server after a fixed number of clicks. But they only have to if the peak usage grows. Peak usage grows, they buy some servers, then go on for some time processing huge amounts of clicks. Things might get even more complicated if they decide to spend the (now) excess processor power on something else.

Fixed, because it happens in the long run. That is, they can't buy another server in response to your additional search.