If United is overselling flights, that means that plenty of full-fare seats are being sold. Bumping does not actually translate into a financial loss for the airline. For example, if full Y is $2500, and the airline must give $400 in vouchers as well as hotel and meals, they still could be making a hefty profit.

For each person on a heavily discounted ticket being bumped, there are other passengers who agree to pay full-fare for a confirmed booking.

But bumping 1000 passengers in such a short period is out of control.