Ok, here's my best tip for how to sell stuff to Buffalo Exchange and I'm sharing it since my geography no longer makes it worthwhile:
When I lived in the northwest valley, I would take weekend trips to the Sun City thrift stores. There are a lot there and they all cluster. The proportion of elderly locals to college kids makes for a gold mine of vintage stuff that hasn't been picked through. Whenever I found stuff that was cool, but didn't fit, I'd buy it for a couple bucks there and then trade it in to Buffalo for maybe $6-8 in credit. I got pretty good at predicting what they'd take and it worked out to be a good line of credit at the store.