what’s the best way to fix this and does anyone know how much it usually costs?

 

cheap route would be a diy, light sanding to clear coat. Make sure paint is clean. And spray more clear coat on it. Chris fix has a good video on painting. You can take it to a body shop where they might charge you a couple hundred to repaint the entire spoiler just depends on the shop

 

Sand, spray, cut, wax.