Maybe an orgy isn't for you if sex is the only part of the evening you would enjoy. In my experience, the clients I've met at orgies always enjoy getting to know the ladies, sharing drinks, snacks, laughs etc, before action takes place.
It's also so much cheaper than it would be if you booked even one single hour with every lady that's present at the orgy, so I wouldn't say it's money wasted. Maybe just not your thing

At least in the context of the industry.
You have to keep in mind the cost for alcohol, food, beverages, the location rental, condoms and lube, every lady's pay as well as paying any staff (bartenders for example), so of course it's not going to cost like 500$