The bottles of gas are around 100 euro each and the switch over vavle is between 120 to 150 euro. the price of copper and fittings are at an all time high due to oil price, that leaves labour charge and VAT.
Does seem so bad to me. After all you are paying a professional to do a job. His training cost money and insurance in that line of work is expensive. However I would take DonKings advice and get another quote to compare, three if possible, this will give you an idea of the going rate.
Under no circumstances use an unregistered installer, they may or may not work to the proper stanards.