Is $650 to fix an aluminum trim piece on the corner of my garage a fair price?

I need to know what to buy, where to buy, and how to replace this trim piece. We had a new deck installed, and the company did a great job but left this piece for the painter, inexplicably. He didn’t fix it. Then we tried having a handyman company, who was doing other work, try to fix it. They ghosted us. I am reasonably handy and think the quoted price is insane. I've confirmed it's aluminum, not vinyl, as all vinyl trim pieces are too small.