Gforce1108, I charge $350 plus cost of parts (no markup). I change everything in the path of the TB, serp belt, cam seal and vacuum pump seal. Also, if the crankshaft seal is leaking, I change it with no additional labor charge. I do charge more if the ALT needs a new pulley. I do grease the bearing set in the Serp Belt Tensioner at no additional charge. I also scan all systems with VCDS and do a print-out. If they want an oil change, I do it at no extra labor, same with transmission oil. I charge $150.00 to remove and clean the Intake, including the head ports.
I only have a few select customers that I do work for... turn down the rest!
In my opinion, the TB can go well beyond 100k miles. But, some other component can give up the ghost much sooner!
May, 2017, the Water Pump locked up on the ALH in my Vanagon at about 50k miles. No warning that I could hear (my hearing is terrible). Luckily, the TB survived the chaos and never jumped time.
Then on the flip-side, the first go around, I only changed the TB and tensioner on my 2000 Jetta allowing all the other parts to go 167k miles without incident.
So, I suppose there's always a bit of a gamble before 100k miles and obviously beyond.