To some degree I think it's fair if the prizes given are representative of the number of entrants.
A case in point....
I'm the current mountain bike hill climb champion of Victoria
(poss all of Australia, unsure if any other states run a hill climb championship).
What did I win? A jersey and a saddle. Both items that the club had left over in the garage from previous events. No money. The top 3 male competitors received cash prizes as well as some bike paraphenalia.
Why do I think this is OK? I was the only female entrant!
My $15 entry fee contributed considerably less to the prize pool that the 60 lots of that amount contributed by the male entrants.
The best solution is to get out there and compete. Bring up the numbers of women riding competitively and then we've got a much better case to put for equal prize money.