I would agree its unreasonable. Software in the US is either the dollar equivalent for pound, I mean here £30 there $30 which is almost half or even worse its cheaper than that. What can you do about it though, if you buy US goods you get hammered by customs and it usually means its even more expensive.
I'm in the Merchant Navy and therefore do a fair bit of importing myself, epsecially from the States due to the very good exchange rate at the moment. UK Customs have been very fair in the past but I can say that if you import you are charged both VAT them import duty on top, which will add 30-35%. Anything above this is pure profit - it's not as if even the instruction books have to be translated!!