I foundAn Honest Cobra Builder and fabricator that does what he say's

[Dominik]

Fabricators and mechanics who work on items where no defined labour times (= costs) are specified are getting harder and harder to find.

Also, my personal experience (as one of such having given up) is that your (often wealthy) clientel get any correspondense drafted by a lawyer to make sure that they get what they pay for. Being detached completely by the work we do they apply non-common sense when it comes to our work. (not that lawyers ever apply common sense - sorry Jamo ;-)
Then their clue-less technical advisors chime in and your next thought is to commit suicide.

I got sued for non-usage of the car when it wasn't delivered in time (by ship) and the client rented an equivalent vehicle instead and sent me the invoice.

Meanwhile, during the built/delay, they have now time to go up and down the internet to get opinions from other "specialists".