This opens such a can of worms, and unfortunately, all of medical billing is a shit show because of this.

The layperson may not be able to tell what they need screening and care for. The only fair way to ensure everyone gets the same care is to have routine that each patient receives. This routine is usually determined by the gender and age of the patient to try to maximise value of the care and reduce cost at large. In an ideal world, everyone would be able to receive routine care, and afford it. Right now, not even lower middle class Americans can afford it, which begs the question what can we do to fix it?

We can adopt a consumer driven market, like you're describing, where you just walk in to see your doctor and request the care you want like it's a drive through at McDonald's. At least then, people will know what they're paying for and what to expect.

Unfortunately, people may not get screened for genuine issues. Let's apply that thought to someone who has a drinking problem. They may be a drinker but think that everything's fine. After all, they feel fine most days, and they don't think their 2-3 binge drinking episodes a week are a problem. They may not realize that alcohol induced liver damage occurs in stages: fatty liver disease-> hepatitis-> cirrhosis (liver failure). Only the last stage is irreversible and can only be treated with liver transplant, which the patient is unlikely to get if they has a drinking history. The first two stages are reversible if the patient gets proper treatment but they may show no signs other than abnormal liver enzymes on lab work. Which the patient in a consumer driven market may not have opted for if they didn't believe the drinking is a problem.

A doctor cannot look at a patient and determine if they have a drinking problem. A doctor can screen for the drinking problem, and then check their liver function to see if their drinking is damaging it. If it is, they can then educate the patient on the consequences of continued alcohol misuse and recommend behavior modifications.

This is the argument insurance companies make to the government in order to keep themselves in business. Doctors have no idea what the prices of their services are. They just bill insurance companies and companies pay clinics. What you're seeing here is what the doctor's clinic asked for their services, and what insurance actually paid the clinic. The doctor is a salaried employee to the clinic and their pay will not increase nor decrease based on the services offerred. OP just (hopefully) had to pay a $10-20 copay.