It is not how lucrative or bountiful your scheme is that motivates people to go for it. It is how realistic it is for them to achieve it with a full realistic stretch that makes it attractive.
If people begin to believe in their first few 'moments of truth' with the scheme that the targets are just impossible to reach ... they will not put in even a bit of their discretionary effort to stretch and reach the goals.
When you design your motivational programs, make them realistic not only rich. The bounty should motivate people to bounce and strive for stretch goal. The program will otherwise rebounce !!!