Vet help!

I took my dog to the vet because she was going bald and has bumps, we didn’t get our usual vet he wasn’t in today. and he was just bad did a horrible job and skin scraping he says he didn’t see anything on the slides. So he just gave us medication to treat the bumps one of them flea and tick meds, for Demodex mange does that sound right? Because it was $120 for two pills and we didn’t trust the vet. Also got antibiotics.