300 is dirt cheap for a basic job.
It needs prep work to sand it down as it being ureathane it needs to have a good amount of flex agent to bend with the panel and not crack off.
Second for a good job you need to remove the panels from the car which means taking the insed panels off to loosen the hanger bolts.
$300 is the pricce for labour of removal and prep
another 350 for paint and 300 for paint application.
700 is a good price anything less and you get what you pay for which includes snading marks ,paint runs, masking lines, fisheyes ,dust in paint ,and the best is insufficent priming and painting causing the finish to flake and chip off with ease of any stone chip