The value of what they provide isn't necessarily it's cost. That's the whole reason we trade. The value of a good is different to different people. If a book i

The value of what they provide isn't necessarily it's cost. That's the whole reason we trade. The value of a good is different to different people. If a book is worth £5 to me, and £1 to you, then if I give you £2.50 for the book we've both gained more than we've lost.