I was going to try some of the Kato ballast but your right it is expensive for small bags. Is there anything else that's close in color say Woodland Scenics ballast in a larger shaker container?
Woodland scenics makes ballast. https://woodlandscenics.woodlandsce...MIy7Sb9qzT9wIVYxbUAR1NSQznEAAYASAAEgLXjvD_BwE
This comes closest to the Kato ballast, but is not an exact match. As long as you are not trying to match a section of track you have ballasted already with the Kato item, you should be all right. Pennsylvania Grey N Scale Ballast 9 oz Bag Part # AZ-1051 $6.39
woodland scenics grey ballast is slightly darker than UniTrack.........I don't have any light grey for comparison.
An excellent article by Thomas M. Tuerke on inexpensively Imitating Kato Ballast: http://thomas.tuerke.net/on/mrr/?thread=1289869264
"The Woodland Scenics products appear to be finely-ground clay or something." It's been my understanding that the woodland scenic stuff isn't very good. I read its crushed walnut shells that's just colored. The walnut shells 'float' when being glued down. Like I said...just what I have read over the years... YMMV .
I think you are correct about the WS.......labels say "contains tree nut by-products" , but I've always had good luck with it.......no floating or anything, and most of what I've ballasted to this point has been NTRAK modules. If it stays in place with all the banging around those get, it's good enough for me. Haven't run into a situation where the WS stuff won't work color-wise........yet. My layout at home is just getting to the track testing stage, so probably no ballast for months. WS will probably be my choice when the time comes........the cost being a big factor. I have about 6 or 7 hundred feet of track to ballast.
Scenic Express sells ballast in several sizes and colors. An added benefit is that it is made from real rock and is non-organic. That means it will not expand due to moisture absorption and will not contract when humidity is low. The real rock tends to stay in place and not float when a water-glue mixture is applied. Less to clean up afterwards. Here is their URL: Scenic Express! The Largest Selection of Scale Model Railroad Scenery on the Web.
I have not purchased from them in a few years, but was happy with them at that time. Hope they are still as good. Looks like they have the same catalog (#17) as I downloaded six years ago.
Arizona Rock and Mineral ballast is available too: https://www.armballast.com/best-model-railroad-scenery-ballast/ That's what I would have used if I hadn't chosen to use Kato Unitrack.