Cost to switch from iPhone 17 Pro to iPhone 17

if this iPhone 17 Pro was purchased directly from Apple within the last 14 days, return for a refund.

Otherwise, sell the iPhone 17 Pro, and buy iPhone 17.

Apple doesn’t usually offer a trade-in on the current models.

How long have you had the one you have? You have 14 days to return it for a refund if you purchased it directly from Apple. After that, it's yours. It is not eligible for trade in. You're welcome to sell it for whatever you can get and use the money to buy something else.