It's been a long time since I worked retail, but we used to get some weirdos at the pet shop - worst was the batsh*t crazy guinea pig breeder. Despite her lack of basic hygiene, odd fashion sense, long, LONG rambling diatribes about the government, her animals were always completely healthy, clean, vaccinated, well-fed and tame. So we continued to buy her guinea pigs.
When I had the record store job we'd get a seriously drunk guy in 2-3 times a week. Always first thing in the morning, he'd be waiting outside, reeking of liquor. Gruff and drunk but mostly polite, he'd spend several hundred dollars at a time on CDs and Vinyl. After a while he opened up a bit, turned out he was a Emergency Room doctor. He'd finish his godawful long shift at 6:00 AM, have a few drinks at home then cab or bike it over to the record store. Nice guy, felt bad for assuming he was just some terminal alcoholic.