The money for sandbaggers is not usually in leagues, it is in tournaments, whether the local weekend tournament or the online virtual ones. I used to participate in one of the virtual tournaments but I was steadily losing money so I decided to study one of the top money winners. What I noticed was this bowler had a unique skill that I did not possess. He could predict when he would bowl good or bad.
I monitored how many brackets this bowler would enter each week. On weeks he only entered a few (1-3) he would bowl sub-500. On weeks when he loaded up to the maximum allowed brackets, he would bowl 650+. He would have just as many bad weeks or more, than good weeks so the average would remain low enough to get some decent handicap. Since I am not able to duplicate that particular skill of knowing when I will bowl good or bad, I decided that I would be donating too much of my money to him so I quit bowling virtual tournaments.
PS - I think that the 1-3 brackets was 'insurance' in case he started off a game with a string of strikes and had a chance at a 300 game.
And for those who do not know what a virtual tournament is, it is a tournament where you are allowed to use your league scores to compete against other bowlers across the country (or world) for weekly position and bracket money. If you bowl in more than one league, you can use each league's scores as a seperate weekly entry.