Just wondering if anyone knows what happens to fees paid to upgrade to Main Cabin Extra if I booked with miles and cancel the ticket.

I recently booked flights with miles and there was not an option to use more miles for Main Cabin Extra so I paid the fee for upgrading. I know if I cancel the tickets I get my miles back but I'm wondering if I'll get either a refund for the money paid for the seat upgrades or trip credit or if I lose it.