what the best but not that expensive 3d modeling software that goes with Unity?
Blender ( http://www.blender.org/ ) is a great open source modeling software with a huge user base.
If you are on the OS/X platform, you can also take a look at Cheetah 3d ( http://www.cheetah3d.com/ ), with one of the most user-friendly interfaces to a 3D modeling programs I have seen so far.
Both programs is well supported by Unity.
i want to tell you 3DS max all my artists tell me its really easy bringing stuff from there into unity and they love the program
though i guess that doesnt answer your question