I've followed this sub for a while now, and I never understood quite clearly the effects of the monkey's paw. However, on a recent discussion, I've seen it explained in a very easy to understand way.

The paw screws with the means by which you get exactly what you wanted.

You wish for 200 pounds, you get 200 pounds, exactly what you wanted, but this money is given as a company compensation for you child's death on a work accident.

So if you wish you could fly, the paw doesn't throw you from a building or makes it so that you fly only one millimeter, it makes it so that you can fly how you wanted, but you realise you have been turned into a pigeon.

The examples aren't great but by thinking it in this way - that the paw screws with the means by which you get exactly what you wanted - it is easier to come up with some interesting stories.