About a year ago, I paid $40 for 100g of reagent grade silver nitrate. Now, the same supplier (Hi-Valley Chemical) is charging $53.82. Not a huge increase, despite the near doubling of the commodity price for silver. Quantity makes a difference here. Small quantities (like 10g) always have a higher price - mostly due to the cost of packaging and documentation.
As to the original question: I've seen potassium bromide recommended as the salt for salt prints. (I think it was in "Keepers of the Light", but I'm not sure.). From what I remember, the speed (as a printing-out paper) may not be that much different, but the image tone will be a bit different. This may be an interesting control, since you could mix the chloride and bromide salts.