OK so first we have to roughly define our terms. There's no official definition, but colloquially Concierge practices still bill insurance they just charge a fee on top of that for things like text/e-mail access, longer appointments, stuff like that. Direct Care is when you don't bill insurance for any of the services you provide.
In the latter case, most people who do that work out networks of imaging centers/labs/specialists/whatever and negotiate prices. For instance, when I was doing that there was an imaging center down the hall from me that offered special cash-only prices to my patients. X-rays were $25, CTs w/o were $250, w/ $500, MRIs w/o were $500. US varied from $70 for AAA screening to $200 for complete abdominal. Read included in those rates.
Labs were done through an agreement with Quest. CBC $5, A1c/lipid/CMP $7 each, PSA $15, Testosterone $20, you get the idea.
49 states allow physician dispensing - basically an in-office pharmacy for your patients only. Doing that, generic medication is surprisingly cheap. I had lots of meds in house that cost less than $1 per month. A z-pack was $4, 30d of flomax was around $8, stuff like that.
Insurance of course had major value for hospitalizations/surgery, but I had specialist that would charge a new patient a flat $125 for the first appointment. Like optometrist would do a diabetic eye exam for $70.