Flight Idle - Campaign medals awarded to civilians are obviously much scarcer than those to service recipients. This can translate into a higher market value, it depends on the civilian status of the individual. Starting with the Boer War, those awarded to war correspondents, for example, have always attracted a hefty premium.
unclenelli the prices on your link are of course for copy medals, and have little relevance to the value of original medals, as awarded. British campaign medals have been named with the recipients' details from Waterloo onwards with one or two exceptions, notably the medals and stars awarded for WW2 service. Officers' gallantry medals (DFC, MC etc) were never issued named, whereas those awarded to other ranks (DFM, MM) etc always were.
Some VCs were forfeited in the late Victorian period, but I believe it was King Edward VII who had the royal warrant altered so that it could no longer be forfeited for any reason.