It's extremely rare. Although I suspect it should be more common. If your salaried employees burn through ~$1500 in the time it takes to interview a candidate then you're kinda saving money by just forking over ~$500 to the candidate to do a take home interview if your employees can then interview less candidates.
Earning $500 for applying to accompany would incentivize people to farm this reward which would clog up the hiring pipeline with people who don't actually want the job.
It's extremely rare. Although I suspect it should be more common. If your salaried employees burn through ~$1500 in the time it takes to interview a candidate then you're kinda saving money by just forking over ~$500 to the candidate to do a take home interview if your employees can then interview less candidates.