It appears that women who wish to donate their eggs for medical research in California are statutorily prohibited from receiving compensation for time, discomfort, and inconvenience and may only receive payment for direct expenses.
The reasons to continue the ban on expanding compensation can be found here which are: (1) lack of knowledge on long-term health consequences; (2) women are not research subjects; and (3) paying women for eggs for research contradicts national recommendations and state policy.
An effort to expand compensation to egg donors for medical research was recently made and can be found here and is currently being reviewed by the California legislature.