That argument doesn't respond to whether it's "strange" that residents are unprofitable. It's just the unsupported assertion that certain unquantified ancillary payments will exceed the unquantified costs of employing and supervising a resident. But clearly they don't, or else hospitals would create more resident positions.
The charge is that hospitals are not creating more residencies in order to collude to drive up doctor salaries. Even if residents were profitable, but less profitable than experienced physicians, it would still be a rational business decision—rather than improper collusion—to hire physicians instead of residents.
