Drywall is not hard, and neither is tile really.
I would pay for things that you really don't want to screw up, like moving a drain in a slab like I had to.
You are going for a bit more than I did though with heated floors and such. I did two bathrooms here in Georgia and came in under 10k because other than said drain, I did the rest myself. Also depends on how valuable your time is to you, people never put that into their cost comparison. If I had paid a lot more it would have been done a lot faster than what it took for me to do it, and I would not have had a part time "job" most every night of the week and weekends.
If you are going to pay that much, make sure you are anal as hell with them so that everything is exactly how you want it before they leave.