I completely disagree with this one. Sometimes you would like to check how cheap is an item compared to shops, and it will be extremely annoying seeing Extra Lives out of stock in Galatic Store, boom one day of no second chances or spend your fuel going to another system, huh?
This can be solved by adding a new number to item that will tell you what is the difference between the galactic shop:
Here it is +13 keys in red, because it is 13 keys more than in galactic shop and red color is usually seen as a loss. Gain could be green or blue.
Then maybe if shop is out of stock of their items then it uses the galactic store items? This way you can’t have something out of stock.