i may be misunderstanding the question here, but the amount of rakeback you get would be dependent on how you spend them.
bronzestar gets you 5FPPs per VPP,
silver gets you 7.5FPPs per VPP,
gold gets you 10FPPs per VPP,
platinum gets you 15FPPs per VPP.
the only constant way you could really determine how much theyre worth would be by the amount of cash you can trade them for in the VIP store.
ie, 1000FPPs gets you a $10 reward, so they would appear to be worth 1c each. however they are worth more when you "bulk buy", ie 40,000FPPs gets you $600, which would make them worth $0.015 ea.
however i wouldnt recomment spending them like this. for example, say you get 1000FPPs. you could trade this for a $10 reward, or you could play 235FPP sunday storm hyper turbo satellites in which 2/6 players get t$11.
playing these instead would give you 4 entrys, and youd only need to place in ONE of them to get MORE than you would from the alternative option- lets be honest, long term youre going to win a lot more than 1/4.
in theory, if 1/3 of the field gets the ticket, the youll be getting a ticket 1/3 of the time if you all opponents are of equal skill level. this would mean youre getting roughly $11 per 705FPP, meaning your FPPs are now worth $0.0156.
moral of the story, learn how to play hypers if you dont already know how (and im sure you do) and spend your fpps like this instead