I am assuming the costs your quoted were in USD and not Canadian dollars.
Umhhh i am going to have to call bullshit on this.
I have an 89 Bonneville LE.
Last summer I replaced the water pump, timing chain cover, timing chain, timing sprockets, serpintine belt, oil pump and every sensor on that side of the motor.
I did all of the work myself with the help of a friend and it cost me a little under 400 dollars including the 200 dollar aluminium timing chain cover.
Maybe if you were having all that work done I could see it costing 750 to a 1000 dollars but just the water pump is easy to do. The part is only 20-30 dollars and there is not very much in the way. You have to drain the radiator first and then remove the serpintine belt and lower radiator hose.
The pulley attached to the water pump has to be removed before some of the lower bolts that attach the water pump to the block/timing chain cover.
I would probably do it for 75-100 dollars not counting parts.
1989 LE Bonne 122,000 miles
Custom Open Element filter system, Strut Tower Brace from 2nd gen bonne
Light Up Pontiac symbol in grill, 16 wheels from newer Bonne/G, performance tires, performance ignition system, Upgraded brakes.