Cost is highly determined by a variety of factors.

I live on the west coast where Bluestone is considered an imported high end product.
The price that you have been quoted above would not even cover our Overhead never mind reaping any profit on the job.

maybe a local professional mason from this forum can help you out better with this.

But even then, prices will vary due to the size of the company, how much insurance they cover, the overhead that they carry, and of course the skill of the craftsmen and the quality of the workmanship.

As another data pt, I just paid roughly $22/sf in southern CT for a walkway (5 x 7.5 ft) set with large square bluestone blocks lined with smaller rectangular bluestone. This was set on a tamped gravel mix, damp portland cement/sand mix over wire mesh, and joined with mortar.

I just finished installing thermal-ed bluestone, in true blue color, installed in mortar over a slab, labor charged $15 a sq foot, stone costs 7.50 a foot and I was told I was a thief, He said "I just had bluestone installed in my house in NJ for 7.50 a foot" So apparently someone in NJ installs bluestone in mortar for as little as 7.50 sq ft. I have been doing this for over 30 yrs, but cannot install bluestone in mortar for that kind of money.

here in n.c it is typically 18-24 for professional intallation, dry laid being cheapest, although some companies can pull off hack jobs for 10 sq' plus materials