I bought this simulator in 2004 for $350. It's a procedural simulator for the Boeing 747. There is no outside scenery but you can interface with MSFS for that.
http://aerowinx.com/html/simulator.html.
I just spent $2000 for a new PC build to run DCS. This doesn't include the cost of the hardware (TM Warthog, TrackIR, Rudder Pedals). $500 is a lot of money for sim software and it would have to offer lots of functionality. However, if it was high enough in quality (Content and Physics), I would atleast consider it.