While creating an Assortment, the creator doesn't select fixed Pricing Tier, it will be set to the default pricing tier. If there are multiple pricing tiers, the user can change the pricing tier to see other pricing. But only creator can change and save it the pricing tier by selecting Display Options once the Assortment has been created.
The pricing tier in any user's profile takes precedence over the default Pricing tier set for the assortment. So the product prices in assortment will be shown in the pricing tier present in user's profile, by default. Ex. A European customer will see prices by default in euro, even if the creator set is to USD by default.
Excel/Share will use the same pricing tier which is being used by the assortment products at any point of time.
If you have more questions, contact firstname.lastname@example.org