I don’t know the terms of their contract, but that wouldn’t fly in a typical contractor setup. You can’t just cut out the contractors labor costs after the fact. I’d be more inclined to give DEFCON the benefit of the doubt if they canceled the entire project earlier on and engaged a different contractor to build an entirely different badge from scratch.
Given that dimitri wasn’t even paid for the firmware(!), my guess is this was low budget. For something of DEFCON’s scale, this can’t really be a “for fun” hacker project if you want to guarantee results. The “for fun” part is ensuring the attendees can all have a good time hacking on the badge, not the people doing the labor.