‘For what shall it profit a man, if he shall gain the whole world?’ That is one of the things which the devil offered to Christ: to gain the whole world, its wealth, its power, and its acclaim; to be king of it all, and Satan would retire to the background, but not a single soul would be saved. To gain the whole world like an old-time emperor, who can survey all around him and say, it's mine.
There are endless stories about people who sold their souls. Spurgeon used to tell one about a man who sold his soul for half a crown, two and sixpence in old money. But he came under conviction in the story and was terrified at what he had done. I've never heard of anyone selling their soul for a few shillings, for a few pence, but I know lots of people who have sold their soul for fame or some degree of fortune, or earthly satisfaction. If you gain the whole world in terms of either wealth or notice or approval – whatever it is – and lose your soul, you have lost all. A single soul is worth more than all the world put together.