Doesn't really anger me, but frustrates the living hell out of me:
Being offered a used pistol worth £220 maximum plus £120 cash for £460 worth of kit that cost £700 to put together Apparently, because the pistol cost £350, it's still worth £350 (quite wrongly) because it's mint, but my rifle and accessories that cost £700 is (quite rightly) only worth £460 maximum, even though it's all mint. Second hand stuff is worth 2/3 of it's original price, even in top condition. I get it, why don't they?