Great contribution, but the money for the riders is in the sponsor contracts. The visibility, especially in Le Tour de France is incredible. So, for instance, Wanty - Gobert team, one of the smallest teams (financially) in this tour, is a Belgian team. And they have riders that try to get in the break away every day. Their sponsor pays them very well, for every minute of TV exposure they are getting that way. Winning the stage is nice, but that's actually not the main goal there. Of course they will try to win, but the exposure is the important part for the sponsor.

Also, after the tour, riders are invited to "after Tour criteriums" in Belgium, Holland, UK, Denmark, etc... These races, are just tours around the main square of a city, and are not real sporting events (the race is mostly planned up front).
The riders get decent amounts of money just for showing up there, and the fans, can watch their Tour heros from up close...
For instance, I know that the city of Aalst in Belgium (where the largest criterium is held in Belgium) pays 50k to 100k for the Tourwinner, just to show up. But other riders, smaller hero's get a nice starting bonus too...

It's all business! ;-)