What you must know is, the prices are like liquid. Whatever the agent decides, that is the price. The bigger the position he/she has e.g. manager, the lower it can be. Since managers of branches review contracts, they often ask the newer agents why they gave such cheap prices.
I understand that the Manager and Assistant Managers make a percentage of all contracts.
When I was in LAX, I booked a compact car for 40 a day. I then asked the guy, "how much is that Cadillac Escallade?" He said "175 a day", then I asked him for 50 a day. He then went into the office and asked the manager, who told him he can do it for 70. The bottom line is, if you don't ask, you wont get.