Why is LH level much higher than FSH level at ovulation?
It is not the absolute plasma levels that are important, it is about their relative differences during the cycle. The steep rise in FSH during the first days induces follicle stimulation. The LH surge at day 12 induces maturation of the egg and stimulates its release (see wiki page). The fact that LH's absolute plasma levels are higher may theoretically have to do with the fact that more LH is needed to elicit its physiolocal response. However, the differences of their relative levels is way more important from a physiological point of view.