Billing is not the only way to assess economic value. If this was the case nurses, PAs, maintenance workers have no economic value since they cannot get benefits directly from what they do.
Also, if there were no residents, you would still need an attending anesthesiologist to be present. I see this argument a lot that residents cost the system money because hospitals are forced to higher attending to supervise them. That can only be the case if residents are actually performing tasks of no economic value, that are not needed, or are redundant. Is this the case in reality? No, we all know residents are a vital part of our health system. A hospital without residents would have to higher someone else to do their job- and the person who would be hired (NP, PA, Attendings) are in all likelihood going to be paid more than the resident doing the job. A good example is the ED, where you have residents doing the same jobs as PAs but getting paid up to 30% less.
Again, we are not asking for 6 figure salaries as a PGY-1, but a salary that is more reflective of our education, skill, and productivity throughout our residency training