The subfloor extra cost may apply to a wood subfloor but certainly not to a concrete slab. Even with a wood subfloor it seems a bit cheap to build a weaker one for non stone tiles. Mortar bleed through is an issue with stone tiles but it's in the vicinity of a few cents per sf for the stone compatible mortar. Stone tile is cut with a wet saw, which is more work to set up and clean vs. score and break. 40% upcharge includes a luxury labor charge because if clients are willing to pay for stone, it's likely they part with money a bit more freely than clients with a tighter budget who chose ceramic tiles instead.

The subcontractor most likely gave you a discount for the contractor cause contractor is supplying him with steady work. $700 your just paying his hourly wage but he is not an Employee , he is a subcontractor small business owner thinking this is too high and believing that $3-4 dollars a sq ft if normal is in correct. Information on Google is way off for what to expect in a real world situation. If a union tile journeyman get paid $35-45 per hour and that shower takes $40 hours his wage alone as an employee if twice the $700 for the week. This is a direct cost for an tile company or small business . You may find someone at a low price but most likely unlicensed , doesn't pay taxes or any overhead no insurance. And not to be found if anything goes wrong. Get the job done right the first time also if tile guy is a one or two man company don't think he doesn't have overhead or expenses . Expenses add up quick go to home depot to buy a part leave spending a $100 or more . I wouldn't charge less than $40 a square foot for tile installation. Cost off living is high really high in California why would I charge less than that. Makes no sense. Just y two sense

The next question is what kind of tile? If the water heater is installed in an attic or over a wood floor you are required to have a pan with a 3/4" diameter drain line to an approved indirect waste receptor or outdoors in a conspicuous place. If it is installed over a floor that is not subject to water damage, such as concrete or ceramic tile it does not require a pan. All water heaters are also required to have a TPRV (Temperature & pressure relief valve) with a full bore drain line to an approved indirect waste receptor or outdoors EXCEPT: in instances where a gravity flow drain line cannot be achieved, such as below grade in a basement, the TPRV may be removed and if it is a gas water heater a "Watts 210 gas valve" is installed, then the gas supply line is run to the Waats 210 gas valve, then to the water heater gas control. In this manner if the temperature in the tank exceeds 210degF or if the pressure exceeds 150psi the Watts 210 gas valve closes and shuts off the gas supply to the burner. When a Watts 210 gas valve is installed you must also go to any convenient location in the structure and install a Pressure Relief Valve on the hot water system where the Pressure Relief Valve can be drained to an approved indirect waste receptor or outdoors. In the case of an electric water heater you only need the pressure relief valve because the upper thermostat in an electric water heater has the required thermal shutdown function.

What is the average price for tile installation for 950 sq. ft.? Owner will complete demo and provide all materials. Installer will provide labor. Owner will also assist with some of labor.