I'd say for your area Alan is probably more on target. Notice that Karl Klein is from Omaha. I've worked in Omaha and the prices there are generally much lower than for NJ. It also depends on the length of the sidewalks, # of steps, what material and equipment is being used etc. Are you using the same type salt for the steps/walks as the driveway? One method would be to figure the cost of material and your % of markup for that. Then figure labor time and rate. Add everything together and that is what you charge.
If I plow the driveway, I charge $5.00 for each 50# bag of material applied plus mark-up the cost of material 50%. If I apply just material I charge the same price for labor that I would charge to plow, plus mark-up the cost of my material.
I only apply bagged material with a commericial walk behind spreader.
We charge the old tried-&-true; labor + materials.
I charge by the bag for how much is actually put down-that way you don't get screwed by a set price. With driveways it won't fluctuate much, but with a commercial parking lot, you're talking LOTS!
I had one customer that used twice as much salt in one application than it did just 3 days earlier! Alot more rain fell, then froze-lots thicker.
I used to charge a set price, but I had to bid it on the high side just in case- worked ok until we had a big storm......