IDL how "preventative health" means I need to pay upfront to maybe save money later

My doctor told me I should get preventative screenings and I was like great idea that makes total sense until I asked how much and he said $400 out of pocket for tests that might find absolutely nothing, and this is the thing about preventative health that nobody talks about, everyone says do it and catch problems early and save money in the long run but the long run assumes I have $400 right now which I definitely don't.

My insurance doesn't cover preventative because they said it's not "medically necessary" until something's already wrong, so I'm supposed to just wait until I'm sick and then pay for treatment that costs ten times more, and that's not prevention that's just waiting for disaster, and I had this whole conversation with my doctor about how important it is to be proactive and he's right I know he's right but he's talking like everyone has $400 lying around for tests they might not even need when I have $400 for rent or $400 for preventative health and I have to pick one.

And here's the thing that really kills me, the whole pitch for preventative health is that it saves money and catch it early and treat it cheap and wait until it's bad and treatment costs thousands, but you need money upfront to save money later and if you don't have money upfront you're just stuck waiting until things get expensive, and it's like they designed a system that only works if you're already financially stable and if you're not then good luck hope nothing goes wrong.

My buddy just found out he has early stage something and caught it through preventative screening and he's fine now and treatment was simple and only $200 total, but he could afford the $400 screening and I can't, so if I have the same thing I won't find out until it's late stage and then treatment costs $20,000, and preventative health saves money but only if you have money to begin with.

Everyone keeps saying "invest in your health" and I'm like cool with what money because I'm already choosing between health insurance and groceries and now you want me to add preventative care on top, and the math just doesn't work.