Hmm, that depends.  Supply and demand rules, most often.  

Example: in 1860, a barrel of flour cost X in Victoria as the Cariboo gold rush gathered momentum.  A stagecoach and stern-wheeler ride away, up the Fraser at Quesnel, BC, that same barrel of flour cost XXX.  In 1898, it happened again, up the Yukon River during the Klondike gold-rush.  Were merchants "overcharging" in Barkerville and Dawson City?  They wouldn't have said so...and guys were lining up to pay the inflated prices...