Fighters are paid according to the worth they bring to the boxing industry! Some of the factors include but not limited to; Marketability Experience Amateur record Pro Record Representation Management Potential Charisma Style of fighting etc... I can write a book on this stuff but I dont want to bore you If you want to get paid well, focus on being a better boxer and set small/major goals. Money is the byproduct of your efforts as a pro boxer. If you are a boxer and you worry too much about the money, you will never achieve greatness!
Or you could go for the big money out Perth way and fight on a Ron Parr show and get $500 per fight, and have to sell tickets/tables to cover opponents costs.
it depends on the promoter, but on average its between $200-300 per scheduled round pre title fights and can be double depending on title and support