Well a bang for the buck is Phoenix RC Sim because (for free) the software keeps being update, i bought V2.5 & now it's V4.0. The flying are being updated by both Phoenix crew & unofficials (users created) & U get downloads from unofficial sites. U get new models & schemes to download. U can create your own flying sites.
So far in 2.5 years i got about 130 models + my personal modifications & 40+ sites.
The physics are realistic & graphics are challenging.
it can suit both beginners & experts, all parameters are adjustable.
includes online playing & several ability contest & a very progresive training mode.
mine came with a Spektrum DX5e for 140$+shipping > a good deal.