Most chinese folks that I know of only buy baby grand, not grand piano, for their kids. A used one in good shape cost about 8k, and it sounds great! If you have to spend 10K to buy a top-notch synth to get similar sound quality, and still have to pay for the instructors, why bother?

If you want to do meaningful comparison, we should put synth and piano of the same price side by side and compare them. I wonder which one's gonna win out :-)

Don't forget that you still have to pay for the instructor! :-)