Websites like It's Worth More, Gizmogo, Gazelle and Decluttr offer cash in exchange for a variety of used electronics.
The deal applies to U.K. shoppers, with U.S. iPhone 16 prices resolutely remaining at full price at most major retailers.
Phones are going for thousands of dollars on online storefronts after Apple and Google took down ByteDance platforms.
The mark-ups come amid President Trump signing an executive order for an 75-day extension for TikTok to sell to U.S. buyers.