If some guys like paying higher prices that is ok with me. Most of these girls are poor and need the money more than we do. Remember, they have babies and parents to support. So don't be too stingy.
If you are looking for cheaper, try the L.A.Cafe in Ermita. The quality is not high , but not bad either. If you offer a girl a lower price, do not say it out loud or let the other girls hear. Why? Because she will lose face and then must say no, even if the poor girl is desperate for a few pesos.
Have fun and try to be generous if you can afford it. No need to spoil them, but don't be a stingy guy either, it will only take the fun out of it.
Warning: these girls are poor and may search your bags while you are asleep. Desperate girls will do desperate things, and so would you in similar circumstances.
P.S. Don't be stupid, use a condom. Teach her that it is the right thing to do. Some of them are young and foolish.