@terryeaton: i know two young "ir" couples (not in person) who did cam shows with swapping partners some ten years ago. (You can still find copies of some of their shows on porn tubes today.) So i guess there are people who would pay for that kind of event.
But ImO 100$ would be too much for only watching, as one can have "not too bad" sex with a ******* for less. Also, if you want to make it a success you should try to suit different tastes, so more than one woman would be advantageous.
i think
@WifeWantBlack6 `s idea of a gangbang is a good one. You can`t predict the performance of a single couple. If you don`t want a bunch of guys "asking" for their money back, a GB can be a solution. i`d recommend two or three ladies, bisexual is a plus, maybe part of a couple where both partners are present, with twelve to 15 active guys and about the same number of spectators. The active participants should not be newcomers to the lifestyle and have an "exhibitionist mind".
Try to propose more people, as it is well-anticipated that not everyone will show up, and make them pay in advance for a better chance it will actually take place.
Try to create trust in the participants by meeting them in person first and setting ground rules together. Also make sure that everyone actively participating has a current STD/STI free status.
Tell the owner of the location beforehand what you are planning on to avoid getting thrown out in between, or worse, having to spend a nite at a police office. And make sure you host in a country/region where this kind of setup is not illegal!
i have still ideas, but i`m getting long...