Best Buy via eBay offers Batman: Return to Arkham for PlayStation 4 or Xbox One for $29.99 with free shipping. (Amazon has it for both consoles for the same price.) That's the lowest price we could find by at least $3, although we saw it for $5 less last month.
Of note, My Best Buy Gamers Club Unlocked members can get it for either console for $23.99 via in-store pickup. (A 2-year membership costs $30.)