i would go to a more 'small time' shop that is trustworthy. In highschool i got quotes for a BL on my first truck(3in) and 4 wheel parts stores quotes $3000 and id have to leave my truck for 9 days(thats how long the process would take). With a local mechanic that i normally brought my truck to, cost roughly $350 and took 2 days.
I was so pissed at the first shop and they quoted the same thing for a suspension lift(just installation) on my 4runner a weeks ago. But, what you can you do? If you don't like it, go elsewhere(or report them to BBB).
Good luck finding a reasonable installtion price. You could always try and tackle it yourself with a friend or two also!