Just a thought on assuming your experiences are the only one, I have never had a dog in my 58 years of life with "winter ear", but I am intelligent enough not to assume that means that isn't it. And I also don't consider finding out what is wrong with your pet to be a "waste of money."
Doing rescue, I have seen mange more times than I care to remember. But scraping can reveal other issues also. So if it clears up, fine. If it seems to be taking too long or not totally healing, more than worth the money.
But let's let vets give you the list of causes: