Supply and demand
Just because you have a supply (a skill, an inventory, a location) that doesn't necessarily mean you are entitled to demand.
The market decides what it wants. You can do your best to influence that choice, but it's never (alas) based on what you happen to already have.
There's a reason that garage sale prices tend to be pretty low.
We can get pretty self-involved on supply, forgetting that nothing works without demand.