I wonder what the best discounted C fare would have been had he simply booked that originally? Compare that to the fare paid + buy-up offered and I venture to guess that there's not that much difference.
I fail to see why that's even remotely an issue. Unless one wants to argue that UA shouldn't sell premium fares (where it makes 90% of its profit on long-haul).
Clearly UA believes that it can sell the seats for fare+$4,400. If it can't, it can cut the buy-up or eventually give them away to a cert / award.