As for restoring cars I got a TA on a rotisserie right now. I have almost all the sheet metal done and I may have $400 into it. both floor pans, trunk drop downs, and toe boards. No rust left at all.
So, you got a shop to completely disassemble you car, put it on a rotisserie, replace the pans and rust..for $400??? I think not, I think $400 only covers the price of the new sheet metal, no labor at all.
If you are doing your car yourself you are not factoring in the labor cost associated with the build, also inexperience causes some jobs to be done twice, how many of us have wasted too many hours learning how to do things the hard (long) way.
You initially posted you thought there was $3k in fluff in Bobs prices, I am saying a reputable shop can not make money doing $15k restorations and supplying a car. If so the market would be flooded with them.
I am in no way defending Bob, but he was not making money doing the work, he only profited by ripping people off on a ponzie type scheme. and now he is broke and unable to complete his obligations.
as for shortcuts, yup, Bob has used what appears to be all of them, and look were it got him, but he still had a staff, and he still had payroll to meet, and shop rent, ect. all of this took $$$, Every day it seems a business goes out from not anticipating how much payroll and operating costs would actually be.
Since this appears to be your first restoration, I wish you luck, and hope it turns out as nice as you are hoping it will, just wait and see how much it costs even doing it yourself. If you keep a spreadsheet of hours and parts I believe you will be surprised, the little thing really do add up fast. and I can say that from many years of experience.