Is there a "moneymaker" roller-coaster in RCT3?

I don't know of any such roller coaster, but I never use the pre-fab coasters (where's the fun in that?). I always try to get the price for each ride as high as I can: check what people are thinking about the ride. If they say "this ride is a great value!" then bump up the price by about 0.50. Go to fast-forward for a while then check if the people are still saying great value. If they are saying "I'm not paying that much to go on X" then you've gone too high. Usually a good roller coaster can go for 5.00-6.00 per ride, although it depends a little on the scenario (sometimes the local residents are cheapskates).

You can also do the same with all the booths. I usually don't take the time to fine-tune the price of booth items; I find I can reliably bump up the price by about 0.30 for all items whenever I build a new stall.

Don't overlook hiring enough janitors. Having a dirty park will lower your park rating significantly, which will cause people to stop coming to your park. I always fully train my janitors and give them the pay raise. They are very efficient after you do this.