Cracked back bumper repair vs. replace? on 2005 Saab 9-3

The plastic (!) back bumper has about a 3 inch crack with a dent below it about 1 inch deep and about 5 inches in diameter. The damage is just below left rear taillights. Body shop told me that it couldn't be repaired and would have to be replaced. Cost estimate: $520 for new bumper; $75 for paint; $300 for 7.5 hours labor.

Asked by for the 2005 Saab 9-3