A couple things that need to be known first:
1) Was the league advertised as "$5,000 First Prize" or something along those lines? If so, you're going to be obligated to have that be first place prize money and can't mess with it.
2) Was there anything said at the meeting about individual awards, such as do you pay only high game, high series, and high average, or is it 1-2-3 in each category?
You didn't say how many teams there are, but I'll give my suggestion based on 14 teams.
Take the amount that each man contributed to the PRIZE FUND (not total dues) for the season, and make that the per-man return for 6th place (one spot above halfway; in a 20 team league, this amount should be for 9th place).
The per-bowler first place money should be very close to the total amount they paid in dues for the season, either a little over or a little under. If I'm paying $20 a week for 35 weeks ($700 total), I would never vote for a list with first place anything less than $650 a bowler, and if it were up to me to make the list, I'd have first be somewhere in the $725-750 range.
With a first place prize and a midpack prize figured as above, you can come up with a slope to fill in the rest of the slots. It's okay to have bigger steps at the top than at the bottom. (A lot of leagues go in $10 a man increments once you get to the lower third of the standings.)
Keep high game, high series, and high average awards the same as each other. (Don't make high average $100, high series $50 and high game $25.) Most Improved should be less than the big three awards.
15# Brunswick Anaconda
15# Ebonite Cyclone
14# T Zone
HG: 279 santioned/300 unsanctioned
177 full season league
171/175 (both halves short-season)
First "Triple Deucey" 3/28/2012: 226-212-202 for 640.