The pump is about $100. Don't know what the book says, but it couldn't possibly take a pro more than 2 hours. I'm slow as molasses in winter and I did mine (not really knowing what I was doing) in 2 or 3. Figure $100/hour = $525 seems too high. Are they doing anything else? Ask them to break out the costs for you.
For a "fair" price you should be paying parts + maybe a small markup and time "by the book" at around $100/hr depending on the location, mechanics experience, etc. If you're paying less you're getting a deal, significantly more and you're getting screwed. Don't nickel-and-dime them on either parts or labor - I'd rather pay a specialist $120 per than some guy at the gas station $80 per - but they should be able to tell you what they're charging you for and why. Look the parts up at Centerline or IAP or Vick's or wherever. If they're charging you 10% more or so, then whatever. If they're charging you like twice on parts, tell them you'll supply the parts. If they're reasonable on the labor and within 10 or 20% on the price of parts though I like to just let them order the parts.
Or do it yourself. I'm talking about what I always do when I take a vehicle to a shop but out of 5 vehicles I've had a total of 5 shop visits in the last 5 years or so......
Anyone know how much time "the book" says this job should take?