Here in Oz, I would think that repair job would go close to the same cost as a new replacement bumper. I know what I would rather have on my ride if I was keeping it. Don't know that I'd feel right selling it without disclosing that it had a patch and paint done.
Current Mistress: 2011 F10 535i - Titan Silver
Retired but not forgotten: E53 X5 4.4L Sport - Space Grey
E46 M3 Individual Convertible - Phoenix Yellow
E39 528 - Glacier Green
E36 328 Convertible - Montreal Blue