You might find it used on eBay or an RCU auction, but probably still won't be cheap. The full version goes for around $200, and I've never seen it go at an auction for much less.

The Real Flight Lite version is quite a bit less, still pretty good.

The problem with FMS and many other less expensive Sims is they don't allow you to plug in wind speed, direction, gusts and thermals, all of which occur in the real world. That being said, if you buy a transmitter (probably $20 on an auction), and FMS with an interface (transmittere to PC), at least you can learn the major control responses, and won't shell out more than about $45 total.
Dennis-