You get more stuff, more status, etc. Or alternatively, penalized, threatened, etc. Whatever it takes to motivate people to do the job. Even if paper money isn't a thing in communist societies (which it still is), money's just a symbol for debt. You're going to get something, somehow, for a job people greatly desire to be done without enough doers and they'll become "indebted" to you disproportionately for doing it.

In Soviet society for instance, you might be provided a nice apartment in central Moscow if you were doing something "important". This assignment would be via your government-controlled employer and their agreements with some other government bureau that officially managed the buildings to dole them out to select people.

So, same deal as anywhere else, just a different mechanism. Higher ration, bigger dacha, jump to the front of the line to get a car, etc.

Compensation is usually not much about how dangerous a job is, though. It's more about how many people are willing to do it for any number of reasons. Some people are just not very risk-adverse, and figure they're going to be fine at a job that is more dangerous. And they'll be compensated at a normal level as long as there are enough such people to fill the need.