Exchange value of a sealed phone

We don't know yet, it hasn't been mentioned by Apple yet. You'd still have to wait for it to be announced by Apple and possibly for Trade In.

See -> Turn the device you have into the one you want -> Apple Trade In - Apple

Get more help:

📞 Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support

or -> Contact Apple Support -> Get Support (apple.com)

If it's been less than 14 days, you can return it, assuming you comply with the appropriate terms - Returns & Refunds - Shopping Help - Apple

Otherwise, you'll have to wait. However, you certainly won't receive the value of the iPhone- generally, trade-in value for an iPhone in good condition is just below half the price. You'll probably get a better deal selling it online.