Material cost of the door is $800.

The owners don't want you there if your not working for them, you had access prior to keys and other sensitive materials so they want you gone...

Will the estimated $12K more in materials be worth it in increased volume? 

The total price using the finish level requested was $6900 for labor and $1500 for materials for a total of $8400 before taxes.

(for my mother)Add master bathroom on second floor (would be placed directly above the kitchen and across the hall from another bathroom)All new systems (2 Zone HVAC, Plumbing (copper pipes), and electrical)I intend to use Spray foam insulationThe entire house would use low-mid tier materials with certain splurges(hardwood, kitchen cabinets)This will not be a rental, I'd live here. 

In regards to what I've done so far as a real estate investor...I'm a part of my local REIA and attending any sub-group meetings, I'm reading a LOT of material and working to find my first deal.  

If that is the case you will be replacing parts every couple of months.Definitely invest in the brass the plastic wears quickly no matter the brand.

What we like to do is provide our PML  the contractors scope of work/ pricing, and provide them with a change order in the event we need other materials.

I probably saved 10k on trim labor and materials alone, but it all pulled together nicely with the modern finishing touches. 

I haven't checked out his materials, but do know he knows his stuff, we did a lot of the same training in the early 2000's.