Even if you’re not a goody goody by nature, the rational behavior for a green card holder at a nuclear lab is to be good as gold, at high cost.
I'm not going to argue that the exact rates are justified, but chances are the person you're replying to was referring to psilocybin assisted therapy in clinical settings. So someone would be signing up to pay for having at least one therapist oversee the process, if not physicians and other staff as well. Factor in their time, operating costs, insurance, etc. it shouldn't be a surprise that the legal option will cost considerably more than buying mushrooms in a paper bag :)
You know, when they talk about "set and setting", that's exactly what they DON'T have in mind.
$3,500 seems like they are catering towards an upper class customer with some kind of premium session. I am certain there would be many in Oregon of all places willing to play shaman for much less. The price of shrooms is not the cost though. How much would you need to get paid to trip sit a stranger for 5-6 hours? I am doing nothing this afternoon and $200 an hour doesn't sound worth it if someone offered $1200 right now. That is a lot to deal with. $3,500 is therapy session with a licensed therapist who is going to be very specialized.
Having now been very frustrated, I did actually follow up and organized my own session through my network. I found a contact who worked in psychedelic research, and who had led sessions with others with psilocybin, had a couple friends join and rented an amazing AirBNB in the woods, and was ready for a night of exploration. The chocolate bars the provider gave us... didn't work. I was left with an upset stomach and nausea, without any of the benefits. Our provider was really into psytrance as well, which if you've never listened to is an acquired taste. They were understanding about it all, but suffice it to say I haven't attempted anything since.
That's a completely ridiculous price, about 300-500 times the "street" price of shrooms. In countries that I have familiarity with (not USA), shrooms have always been "technically illegal" drug which law enforcement never actually actively enforced, either formally through procedure (with doses below 100 grams considered fine-only territory), or informally, because the cops just don't take it seriously.
So to me it seems like you're choosing to follow the law even though it would not hurt anyone and you would not get into any trouble, just out of pure principle. That's actually quite impressive.