I've had some insightful lessons on this within my own experience. I used the local urgent care places for DOT physicals when I was an owner operator, and paying for them out of pocket. Twenty years ago, the docs were older guys winding down at the end of their careers, pretty sharp. Quality deteriorated over time, last visit I got a rookie who was a complete twit, I said no more, and started paying three times as much to have my primary care doctor certify me.
When my wife had neuropathy issues in both legs 20 years ago, local talent (covered by our insurance) recommended a procedure that would have partially paralyzed both feet. I got a second opinion from a nationally prominent neurosurgeon, he ended up doing minimally invasive nerve releases, with excellent results. He also charged $8000 for each procedure, and did not accept insurance, took a check up front.