Sounds like the same risk as this situation of reusing them.

We sterilize plenty of other common tools like scalpels so that doesn't seem like a valid reason. Obviously the disposable design is not even an adequate solution to the risk of cross contamination. I would imagine if it were a real concern you could easily add something like a color changing strip that would indicate whether the needle has been autoclaved since its last use without rendering it useless.

Prions aren't destroyed by autoclave