This is a problem from the perspective of the customer. Company X delivered a substandard product based on a fix bid. The customer then had to turn around and pay 10 weeks of hourly fees to this guy to finish it.
Presumably, if magic of value pricing was realized X would be incentivized to finish it.
Pretty unprofessional on X's part I'd say, so I understand why the OP nearly lost it.
I think that just highlights the downside of fixed bids, value based or not, that the author ignores. You come out ahead and are incentivized to finish early, but are deincentivized to do any additional work if you go past your costs plus margin
The customer found someone to do the work and was willing to pay for it. If he had his customer's interests at heart, his objection should have ended the moment the customer made a decision. No need to "lose it".
Presumably, if magic of value pricing was realized X would be incentivized to finish it.
Pretty unprofessional on X's part I'd say, so I understand why the OP nearly lost it.