I have a question that is predicated on the open-ended tag. I believe that the following fulfils the requirements yet my instincts tell me it will get closed.
In the absence of a sandbox facility on Puzzling, I have the following
Will the following question stand? If you think not, what improvements do you suggest?
Here it is:
Wizards sell magic woo-woo to Muggles. For example you can buy a spell to rid your house of mice or place a curse on an enemy. Wizards only accept gold (Au) in payment.
A spell is based on a certain amount of woo-woo. It lasts until you use the spell. You can use the woo-woo towards any spell you like. Wizards measure woo-woo in drogs.
You are a Muggle and your shoe has a hole in it. The local cobbler has a very long queue and you need the repair to be done quickly. You visit your neighbourhood wizard.
The wizard states that a spell to repair your shoe will require 10 drogs. At today's prices, he is charging 1 puddle of gold per drog of woo-woo.
Why does the wizard need gold?
What can you deduce about the availability of woo-woo?
The question is open-ended because I do not know the best answer but I have ideas about it.
All units are arbitrary.