I have a similar question related to this. What happens if you switch characters while having items in your store cart?
For example, I want to add say an extra Legendary Slot, but it only shows up the store for my character that has access to legendary items. If try to search for it on characters that are below level and haven't accessed their first legendaries it says there is nothing available.
Now, I switch to my Lore-Master (a character that is only about level 35, and thus doesn't have access to legendary slots in the store), the legendary slot is now still in the cart (from the previous character I switched from.) On the new character I want to buy several mile-stones, and the steed of the lore-master, so I add those to the cart as well.
Ok, so what will happen if I try to 'purchase'?