I see a few good ways to do this. First and foremost though, aside from whatever fine structure is implemented, no matter what format is chosen it has to be stipulated that all three sets must be played and completed. If a player chooses to forfeit at any time, he forfeits any and all monies earned from all of the sets, including any previous ones.
The first way to do this is to play each set with the winner getting $1600 and the loser getting $400. If it goes 3-0, the winner will have earned $4800, and the loser $1200. If it goes 2-1, the winner will have earned $3600, and the loser $2400. This way they both earn pretty good money, particularly if the sets are split.
The second method helps to create a little more separation between what the winner and loser end up earning. Each set is played with the winner getting $1350, and the loser getting $350. Whoever has won the majority of the sets when it is over gets a $900 bonus. So if it goes 3-0, then the winner will take $4950, and the loser $1050. If it goes 2-1, then the winner will take $3950, and the loser $2050. At a minimum the winner will be winning about double what the loser takes, and if it is a sweep, nearly five times more.
Another idea that can be used with either of the above options is to secure an advertiser to sponsor a bonus of say $1000 (or whatever advertising charge is appropriate considering the risk) if one of the players can sweep all three sets, similar to the way that advertisers sponsor a prize for a hole in one in golf, or for a maximum 147 break in a snooker. I would think that this would be pretty appealing to sponsors because the chances of a sweep are fairly low and they may just end up getting their advertising for free. Obviously you would want it prepaid and just refund it if it doesn't happen.
Or you could structure it where you negotiate an amount you keep for yourselves as an advertising fee if there is no sweep, and you refund the rest. Of course the "usual" advertising rate that would have been charged would lay somewhere between these two numbers, and because of the risk involved they are actually paying less than usual if there is no sweep (and you earn a few bucks), and they are paying more than usual if there is a sweep, and it all averages out. Any number of ways you could work this.
Or you could just have the advertiser sponsor the bonus money for the overall winner instead of the sweep, which would work especially well with the first method.
Another way yet to work this is to have the advertiser sponsor a bonus for both. Say $300 for the person that takes the sets by a 2-1 majority, and an additional $700 if they can take it in a 3-0 sweep. Obviously you use whatever numbers are appropriate based on what you usually charge for advertising, with your "usual" rate falling somewhere between the two but probably closer the "majority win" number. Whether they sponsor just for a sweep, or just for the overall win, or for an overall win and also for a sweep, they could be billed as your "bonus money" sponsor for the event.
Whatever it turns out to be it has to be able to be made clear in a single sentence. I am leaning towards each guy getting a $1000 guaranteed and playing for $1000 a set with $1000 bonus to the winner. If I do find sponsors I'll probably use the money to help outrun the $6000 plus expenses and production costs we will already be stuck.