Why do charity shops charge so much for things they sell?

Ive noticed that over the past few years the price of clothes etc has shot up. i was in my local red cross chairty shop last saturday and the jeans were £5.50, shoes £4.50, and tops £4,20. the thing is you can buy the same items in primark for less and at least they dont smell. they get things for free, dont have to pay their staff as its voluntary work, i just cant understand why they have to charge so much. a barnados shop has opened in the city centre that sells really modern clothing, bags and shoes and even in there you could by the same things cheaper from the actual shop they came from. i mean charging £9.50 for a pair of worn jeans is taking the pi**. i know where id shop and its not in a charity shop. im sorry but if they brought the prices down a bit they might actually get customers. i took some of my sons old clothes into one near my house and the next day i went in for a book and they all have £3.00 tags on them!! £1.00 yes but not £3.00. its cheaper at primark!!!!!
Answer
They want to raise money for the charity.