"I ended up buying 60 tablets of alprazolam, just because I could"

Same thing on the Texas/Mexico border. I was in Eagle Pass a few years ago. We decided to cross over to Piedras Negras to be tourists. Our pharmacy experience was the same – we could (and did) buy just about anything we wanted without an RX. The difference was that the pharmacist explained to us that we needed to go to the nearby market and buy some tequila, a woven blanket, or a pottery burrow so we would have something to declare at the border. If we said “yes, we are bringing back these things” the border agent wouldn’t be suspicious that a few Americans had spent the day in Mexico but didn’t bring anything back. Worked like a charm. I even like the woven blanket and use it in the living room to keep our dog off the leather sofa.