6 hours isnt too far off, seeing as the shower valve you have there has about 5x the piping of a typical shower valve+shower head. Also 5x the fittings and copper pipe, which you didnt state he asked for more material cost. Then theres another 20-30 mins of messin with trim and handles once the tile guys are done, and calibrating the temperature controls with a digital gauge..
so, thats not so far off. you want extras, you pay for extras.. 6 hours in a new house build of 200-500k is peanuts. Do it once, do it right.
(and yes i am a plumber)
if it aint broke, tweak it!!
currently on FiOS (kick aZZ!)