I am assuming that you are talking for something like that:
The $30 simulators that you reffer to on E-Bay are basically USB joystick in a form of dummy RC Radio Tx. The unit is very usefull to control a simulator and many people are quite happy with it. The software included is the free FMS simulator. $30 is a good price for the USB control unit. The FMS simulator is nice to start but has some limitations in the flight model. If you do not want to pay $200, you can try ClearView RC sim from
http://rcflightsim.com , there is a free trial and cost $30 to buy if you like it. It flies as good as any $200 sim, but lack some bells and wistles compating to $200 sims.
Stefan
http://rcflightsim.com