Or they somehow want to price things off eBay prices. Bro, you are a thrift store. You aren't some place that should be trying to get the absolute most out of an item.
Price it vaguely on what people might pay for some used, unwashed, beat to hell thing. If someone thinks they can get more by selling it online, that's fine. That's on them. You don't have to compete with them. Turnover of items is more important than the most money on that old glass cup.