Door stop

Why is it that when you buy one thing you always have to buy another unthought of thing? We had a door made into the garage but it slams shut as it's a fire door, so now I've had to buy a doorstop. Luckily he was a bargain from Homebase for £10. All the others I've seen have been £20 or so. As you see I've not had a very exciting day apart from.....booking a holiday to Cyprus soon. Yay!