Why am I not getting the listed prize money in Gran Turismo 3?
If it is anything to you, in Gran Turismo, any prize money from a race remains consistent. If you get 1,500,000 the first time you will get it every time, assuming you finish in the same position.
If you are getting 1,200,000 from a race that says you get 1,500,000 for that position it is most likely a typo of some kind. I can't say for certain being on the PAL release of GT3, but that is the most plausible option.