That is entirely up to you... you need to decide if you're going to pick up enough 3D work to justify the cost. If you just want to dabble in modeling there are cheaper (even free) alternatives.
I'm primarily a hobbist, although I do get to use Maya occassionaly at work. I'm a graphic artist in the U.S. Navy.
AIM: mhcannonDMC
"If you love your job, you'll never work another day in your life."