As a seller, the onus is on you to get the pricing right. If I don't update my convention stock, I get scooped as well. It is the law of the comic jungle.
I have had friends pull out AF 15s and other Marvel SA keys at garage sales for next to nothing ($20 for a 4.0/4.5 AF 15 a couple of years ago), and another local seller scored a bunch of GA books (including a low grade Tec #38) a few years back for $1 apiece. FWIW, when the ASM 688 JSC Lizard variant was first hitting $1,000 online, there were local stores selling them for $5 in variant overstock bins........