I think you're seeing how the ACA mandated free vaccines, so the $300 gets billed to your health insurance, then your insurance negotiates it down to $30. If you don't have insurance, it's the sticker price.
No, this is a loss leader / community benefit these corporations participate in. They'll attempt to be reimbursed through insurance, but also offer it to the uninsured.
> *FOR FREE FLU SHOTS & 14 NO-COST VACCINES: Select vaccines at no cost with most insurance. Eligibility varies by patient and insurance plan. Eligible patients will not pay any copayments unless otherwise required by their plan, including Medicare Part B. Availability varies by state based on regulations...
That doesn't sound like it's free if you're uninsured. Or at least that don't advertise that.
it's never the sticker for cash, if you pay cash you will get the same rate the insurance companies get. Why would a clinic turn down the sale? Just shop around and say you'll be paying cash.