Plans, account access, and transaction costs
The app itself is $0 per month and does not require a paid Square plan or Square Online website. The product page says a Square account is prompted when a user wants to save photos, sync them to Square items, or create a Square Online Checkout link. If the app-created payment link results in an online sale, Square's U.S. Payment Links page lists no monthly fee and a 3.3% + $0.30 online transaction fee for new Square customers; Afterpay transactions are listed at 6% + $0.30. Those are payment-processing charges, not a Photo Studio fee, and high-volume custom pricing may apply.
