It greatly depends on what shocks you fit!! I fitted Bilstein shocks (cost $400 for all 4) and fitted them myself, with a rented spring compressor, total time was 2 hours. So assume a garage charges $140 an hour, you are looking at about $300 for the mechanics time plus the cost of the shocks.., Total around $700 to $800. Its a surprisingly easy job to do yourself if you rent a spring compressor (Autozone rented it for free) and have a jack to raise the car (one wheel at a time), no special tools needed except the spring compressor.
Gary