There is next to no money in pro cycling. Sure there are a few very very elite riders that make millions, maybe 10 to 20 of those. There are also the other 160 riders that start a grand tour. Read some of the documentation USADA put out on Lance. Not about the doping, but like Dave Zabriskie was a legit world class pro, he raced the Tour, and I think they listed is salary in those early years as like $24k. Another name that comes to mind, Gilberto Simoni, as fine a climber as has been, a grand tour winner, in his earlier years he worked as a bike shop mechanic in the off season to pay his bills.

There is no TV money for the teams. The team sponsorships aren't even guaranteed for any serious time. It's all about individual results in what is really a team sport. And then the best years are during the college years for everything else, close to no pros actually have college degrees or anything. Worse, I can't think of a pro that came out of college and ever did anything other than domestic racing. I mean, the team bikes are technically supposed to go back to the sponsors according to most deals but everybody just sort of knows that a lot of riders sell them to supplement their income, there are even web stores that specialize in it.

Cheating is cheating, be it chemical or mechanical or whatever, but cycling (like skiing, track and field, etc) is a perfect storm for it. If you do it and don't get caught, you can get rich, like life changing rich. If you wash out, not just did you lose what little paying gig you had, but you've probably got limited options outside of cycling. I'd argue that other than the love of the sport and sportsmanship, there are a lot of cyclists in a certain age range that have no reason not to cheat one way or another.