Yes, the B&C team not being able to do the restoration themselves, obviously has a huge bearing on whether or not they are able to make a profit on resale - having to pay a garage / professional restorer to do the work is naturally going to be very expensive.
Joe Public buying a project car and taking five years over the work, will not feasibly be able to catalogue every hour spent on it, so I imagine just keeps a record of money spent on parts etc.
As said before, it’s done for the love of the car, and the personal satisfaction of actually being able to do it.