Personally I like to know what I'm paying when I enter the room. spending 10 minutes negotiating eats into my time and has the risk of tainting the atmosphere of the session for one or both parties involved.
Women negotiating their own price sounds good in theory but I think it would cause a mess logistically. I pay my $$$ at the front desk, pick an attendant, go to the room, I want a bs and we can't agree on a price. Now what? Different attendants are sent in until I find someone who will do what I want for the price I want? I leave and get my money back? I'm stuck with my choice, we barter for 30 minutes and nothing happens? And I'm sure there are many other scenarios that would cause everyone grief if it worked that way, including getting into the room with someone you've enjoyed previously to find out her price has gone up $25 since the last time you were in.
Fix the prices. If you get great service, you can always tip the attendant to show your appreciation. For sure you will be back and ask for her which works to everyone's benefit. You may even advertise on her behalf by posting a good review on massageplanet.net. If you feel you didn't get value for your dollar, go somewhere else next time or choose a different attendant if you return to the same establishment.