The number of channels you can use simultaneously does not only depend on how much money you are willing to spend, it is also limited by physics. Any transmitter radiates both the
wanted frequency and many unwanted ("spurious") frequencies that interfere with other signals. It is not easy to calculate interference-free frequencies. The more precisely a transmitter operates, the less "dirt" it will emit and the more expensive it will be. Affordable systems today usually allow you to use six to eight channels simultaneously within the same VHF or UHF band.