When I worked for myself doing tile, I charged $5/sqft labor, $20 per sheet underlayment installed (materials included), added a couple bucks per bag of thinset and grout to cover wear and tear on buckets, drills, mixers, trowels, floats, sponges. I typically bought all of the materials mainly for quality control.
I always used permabase for underlayment. 3'x5' just under $10 per sheet. (I hate the hardibacker. It is compressed paper. I know they say it wont degrade or swell, but I dont believe it. It dosent cut for crap and dosent screw down very well)
I always used Mapei ultra flex 2 thinset. Its like $25 per 50# bag that usually covers 75sqft. Or used the stuff that you can put in the latex additive for exterior.
I use either Mapei or TEC grout. TEC is smoother. I hate Laticrete brand grout, it eats my hands up. 25# of grout usually covers 100 sqft of 12x12 tile with 3/16 grout joints.
I also warrantied my work. Only call backs I ever had is when somebody dropped something heavy and broke a tile.
Make sure they use SCREWS. Never nails.