What’s an “upcharge?”
When the waiter informs you that it will be an extra $3 to guaranty that no eel or shrimp come with the “sushi combo” lunch special (true).
(I took my chances, and declined to pay it).
So, what’s a “downcharge?”
When the cashier at The Wedge reminds you that you have $5 in store coupons that expire at the end of the month, and encourages you to apply them to your current purchase.
P.S.: also qualifying as an “upcharge,” at least in my book: an airline fee to pre-select your seats (see, “Calling Sun Country’s Bluff“).