How much is a pound of weed on the east coast(New York), west coast(San Fransisco) and the midwest(St. Louis)?

I'm doing a comparitive essay to find out what influences the prices of marijuana but I don't know what the full spectrum of prices is. I understand that there are different grades/qualities of weed but for the papers sake let's say that the prices are for a midgrade weed like Afghan kush or White Widow.