I think it makes a big difference as what your contracts say, all mine are 2" start plow & every 2" after. A 6.5" snow means I plow 3 times example 1 lot I do is $750.00 every 2" if I salt it's only $450.00 & if I salt the whole lot the snow might not stick & only get to plow twice. So I plow 3 times =$2250.00 & salt the entrance, exits & drives twice $250.00 & salt entire lot 1 time for $450.00. Total is $2950.00 now that's making the most $$$$$ out of a snow. If I plow & salt twice it's only worth $2400.00. I understand each & every place is different so plow triggers & contracts are different as to location state to state.
Now if it's only a 1.5" snow I do salt so in that regard I make $450.00 so if you don't have a salt spreader you're not making easy money for the taking .
Naturally it will vary from company to company too. It is less overhead to send out your crews to salt than to plow. The profit margin is higher salting than plowing.
You might need 5 drivers to plow your route(s), but only 2 to just salt them.
I was actually quoting SnoJob, but also agreeing with him
If a 3" - 4" storm is forecasted, we pre salt the entire lot. Then plow at the 2" trigger. Then salt again. Then plow the remainder, followed by another salting. All of these saltings are aimed at preventing the bond from forming, and preventing hardpack. We charge "per application" for salt. It might be a light application, or a heavy one, it is at our descretion. We typically apply light, unless conditions (temps) call for a heavy one.
The main gist is that salting is a profit center that many plowers miss out on. That we all agree on.