What’s with the bait and switch?

Went to upgrade my iPhone 14 today. On the initial page showing all the available phones, it shows I can get an iPhone 17 for $4.16/month for 24 months. My trade in shows $830 credit on the trade in page. Then I go to check out and it’s $12.50/month and only $630 trade in credit. What gives? *this was with me being logged into my account and going through the trade-in steps.