I understand your frustration.
Unfortunately however, this is the internet and players disconnecting during a game is nothing new. It will always be problem, regardless of what the game is. Do yourself a favor and don't stress over what other people do. Just worry about you and play the game how you think it should be played. If you'll notice, all competitive modes are single player because when it really come down to it, that's all that matters. Don't be regretful about spending your $30. That's money that can be used in the single player tournaments to better your scores and earn more money. Multiplayer is just a nice bonus that doesn't absolutely have the need to exist considering the format of the site in the first place. It's World Golf Tour, not World Golf Multiplayer Hangout. Considering the numerous documented technical issues that the multiplayer game has, it shouldn't be ranking people to begin with, but I digress.
The person(s) quitting to artificially lower their average score gains nothing but stiffer competition. You even said it yourself, they're just cheating themselves in the long run. Let them quit all they want and get to master status in the first day. Then you can sit back and have a hearty laugh while they get the snot beat out of them by the likes of tibbets, AvatarLee & company on a weekly basis and never so much as even sniff a single credit of prize winnings. Some people would consider just being in the master tier a penalty in itself because of the quality of talent that already resides in it's upper echelon.
wirenut481: bet we would have less masters if you did this
Be careful what you wish for. :-) Having less masters actually works against you because that would mean there would be more Pros that can actually take your cut of the prize money instead of having a snowball's chance in hell at ours.
So, the next time a player disconnects on you, take comfort in the fact that you will ultimately have the last laugh because those players are soon going to be in a world of hurt when they are forced to play with the legitimate best of the best.