Comment: The reason that Apple charges different retail prices in each market is due to the differences in wholesale prices charged in each market by the major labels. Apple could use this as leverage against the labels to lower their prices in all major EU markets

Apple today announced that within six months it will lower the prices it charges for music on its UK iTunes Store to match the already standardised pricing on iTunes across Europe in Austria, Belgium, Denmark, Germany, Finland, France, Greece, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Sweden, Switzerland and Spain. Apple currently must pay some record labels more to distribute their music in the UK than it pays them to distribute the same music elsewhere in Europe. Apple will reconsider its continuing relationship in the UK with any record label that does not lower its wholesale prices in the UK to the pan-European level within six months.

source: http://www.apple.com/uk/pr/2008/01/080109_itunespricing.html