1) You can't turn an operating room immediately. A 1hr surgery requires significant prep time _AND_ cleaning time. These rooms are used for many different kinds of surgeries — changing everything takes time. To make matters worse, each surgeon has their own preferred set up, and it needs to match that.
2) All medical supplies are expensive in part because your body is pretty sensitive, and you need to be careful about what's in there, but also because doctors almost always have _COMPLETE_ control over what equipment they use ... including screw and tool brands. This means that hospitals have little-to-no leverage to get lower prices. This is particularly true for implants & other complicated equipment.
3) Insured people subsidize the uninsured.