With Hock Shops I have found that most price the goods at 2/3 higher than what they paid, example if they paid $100 the item will be on sale for $300. I often offer half the marked price, especially if the item has been in the shop for a few weeks, often I get the item for 2/3 of the marked price.
My local shop has a Studio Projects mic priced above what I can buy a new one for (they probably checked retail online but nobody pays that), It's been there for 2 months, if it's there next time I go in I am going to offer a stupid price for it just on the chance I may get it.
Alan.