I have my own landscaping company, fully insured. Granted I am in a different area than you, but assuming the ground is relatively level, removing/disposing of the sod, and full access with equipment I would charge around $1000 for installing the stone. Then 6"x6" treated border would be almost $320 in materials alone, totaling $1320 plus labor to install the 6"x6" border. So $1500 isn't that far off.
-About 6.5 yards of stone x $45/yard (included is my cost of stone, time to get stone, fuel, delivery, small markup if I need more than estimated, etc) = $292
-Compacting = $100
-Labor for rock/skidsteer cost = $450
-Removal/disposal of sod = $150
- 6"x6" treated lumber, nails, etc = $320
- Installing 6"x6" = $120
Project total: $1422, plus tax (5%) = $1493.60