You know, I've recently seen here on HN complaints about "product substitution" at Amazon - getting, not what you ordered, but something that Amazon thinks is equivalent. I'm not sure medical supplies is where you want that to happen. I'm therefore not sure that the comparison of price to Amazon is fair. Note well: Yes, hospitals also gouge you. I am not claiming otherwise.
The important part is being over-charged 900% over retail price, not the exact retailer you buy it from.
Also, it's a sling, not an anti-HIV drug. Hardly a "medical supply".