Depends on if you hire full time or part time hygienists. Benefits and such all factor in there.
That hour of e.g.
4BWX ($45) + Prophy ($120) = $165.
Even if you pay your hygienist $50, you're still making over $100 an hour off that cleaning. Overall, it's very profitable. Sure, not as much as an implant or denture case but while the dentist is doing the more "important" procedures, the prophies are constantly happening in the background. If you have 25 patients, that's around $1750-2875 a day, give or take some x-rays and stuff in this scenario. Not a bad day.