Do these repairs and costs sound reasonable?

We weren't aware anything was wrong with the car, but took it in to be inspected so we could sell it. A potential buyer heard a soft scraping noise.

We received a quote of $550 for used rear end, $445.48 for axle housing, $75.96 for gear oil and $445.48 for labor to fix the rear end. Total of $1,146.44. I know nothing about cars and am always paranoid about being taken advantage of. Thanks for any guidance.