Rudy loooves deer antlers - which is good because you are right, they are quite the expensive chew toy! The lady at the store told me that not all dogs like them, so soak them in chicken stock overnight and then pat dry, or rub peanut butter on them. Rudy is a massive chewer so I did not do that, but might b worth a shot?
I must say those slices are massive though. Maybe they just can't get their mouths comfortably around them?