Some website might have a general gist. Like in Md crabcakes and crabs normally say market price and normally you can find a normal price it is at most places $10-15 crabcake sand, $25-30 crabcake dinner etc. I think some areas have a general price on things. Maybe chow would be a good place to find that out.
I do think it depends on where you are how far it is for them to get that item, it will be cheaper if it is closer for some things. I am sure MD crabs are pricier in other places than the Eastern Shore, not just because the Market holds that but because that is what it costs them. But it may be what the market holds in that area.
I think it probably really depends on how much they buy and sell regularly, the more they regularly buy and sell the better deals they will get for the product.
I don't think so - I think it varies from restaurant to restaurant due to a few factors.
Some of them would be:
Type of food
Type of preparation
Plus overhead and stuff. I think that it's there because the price the restaurant is paying for those items can vary more often than the rest of the food on the menus, which are more stable.