Yes this seems to be a problem with alot of people who can't get rid of scabies, it seems the medications they give you at the pharmacy do not even penetrate the skin so the scabies ultimately are not killed, and with scabies you have to kill the whole cycle within one treatment or they will just spread again. Your feet and hands are also the most common areas that people get reinfected from scabies on. Try soaking your feet in baking soda which will softened up your soles and its good for the skin, you can also take baking soda baths to ease the itching associated with scabies.

You are correct, it seems the mites more and more are becoming resistant to treatments like permethrin which are given out and also dangerous, the strains likely evolved and are strong enough that it doesn't phase them. Ofcourse all strains of scabies are never the same as you pointed out. I found this out when I was stupid enough to try permethrin many times and the stuff never even worked! Was very frustrating point in my life having to explain this to people who just wouldnt listen.