so a class with 100 racers only pays only the top 3...wtf is up with that? Either those three guys are living like rock stars, or the greedy race organizers are.
Seriously though, just keep at it by going to every race you can. Chances are that the same small group of guys shows up for every race and ends up winning every time. If the gap is only a minute at the end, you should be able to go all out to hang with the leaders at the beginning. This will build your physical strength and pain tolerance. you might blow up early on, but if there's no difference between 5th and last, then just write it off as a learning experience. Try to stay tight with the leaders as long as you can and learn their strengths and weaknesses, then you can know to drop the sprinters on a climb, bomb past pure climbers on a technical descent, etc. Plus if you hang tight with these guys, you can follow their lines and really make your move if they make a mistake or have a mechanical. Also, nobody is perfect all the time. some of the top riders are bound to have bad days, so if you're there on that day, the podium spot will be yours. To summarize: Ride harder, ride smarter, and ride often!