Share 'Pricing'

It does affect the sale, so how to price without costing yourself anything? What an item's worth is what the market will bear, imo, as opposed to what it should be sold for. What think? Btw, when I got home after buying something a week ago, the sticker on it showed a lower price than what I'd paid. That left a bad taste in my mouth. I understand that prices do go up, but I couldn't help feeling…