take this scenario.
You aren't the best applicant for derm. Your only match is a residency program that you have to pay for. Derms make more than most specialties and that cost is 1 years salary, so to you, its still a sound investment. Other derm programs gradually shift to this pay for models as they see the potential revenue. This model gradually spreads to all the high paying competitive specialties. Are people going not apply to them? Nope because you still get a great return on your investment. Eventually, this could trickle down to the less competitive specialties.