A good trigger job on a 1911 requires an experienced gunsmith with lots of patience and the right tools.
Not everyone can do it right.
The big question to ask: "If I want a light, crisp trigger action, will you shorten or soften any springs to achieve it?"
A "yes" answer tells you to find someone else to do the job.
A 1911 trigger job should be a matter only of resetting sear-contact angles and smoothing with polishing stones.
Brownells opines that it should cost between $60.00 and $100.00, which averages out to $80.00.
If the job is really good, and the 'smith delivers the pull weight that you specified, I suggest that $100.00 would be fair.
The last time I had one done was so long ago that a really good, three-and-a-half-pound trigger cost me about $30.00!
(I've done my own, and my work is OK, but I'm nowhere near as good as an experienced 'smith. I suggest that you can learn to do it, if you have lots of patience.)