If Congress were forced to forwgo pay and perks during shutdowns, there would be fewer of them
They're more concerned with keeping their jobs in the first place. For a large number of Republicans, that means shutting down the government as much as possible. It's explicitly what their constituents want them to do.
Those aren't a majority, but the remaining Republicans are reluctant to work with Democrats to get majority support. Much of the Republican platform consists of denying Democratic priorities, and collaborating with Democrats could cost them their job in the next primary. Primaries begin in just a few months.
More than the paycheck, the lose the ability to run the country if they lose their jobs. You don't get into politics for a job that pays little more than a recent college grad in Silicon Valley. You get into it so that you get to run the country your way.
Now, if you told them that they could not be a candidate for office while any part of the government was shut down, that might move some action. But then, many of them would be perfectly happy to sacrifice their own jobs if it would get some other people out of office.