“Save up to 35% on mattresses.”
A discount banner is not a hero. The page now teaches new visitors that price is the reason to choose Casper. When the next competitor offers 40%, there's nothing else above the fold to fall back on.
“Restore a sleep-promise hero: "The mattress engineered to keep you cool all night. Try it 100 nights, return it any time."”
A category leader's hero should sell the outcome (cool sleep, low-risk trial), not the price. Discount goes in the announcement bar where it adds urgency without becoming the entire message.