Xanthan IS expensive! I think the last bag of it I bought was around $12. But when you realize that it takes just a tiny amount of it to thicken a sauce, that little bag of it will probably last for at least a year or two, it's a worthwhile investment. I think the most I've ever used at one time was around 1 tsp, and that was to thicken at least a pint of gravy.


Note on using xanthan: Best way to add xanthan to a sauce that I've found is to make a roux from it so it doesn't clump (easiest way to make the roux is to mix it into a bit of olive oil - approximately equal amounts xanthan and oil), then pour the roux into the already heated sauce/gravy you want to thicken. Most directions say to whisk it in, and that works well enough for a small amount of sauce, but when making a pot of gravy, I've found that I get the most thickening effect from it if I use a stick blender on it to fully emulsify the xanthan into the larger amount of gravy. I usually need to transfer the heated gravy to a deep mixing bowl for this step, so it doesn't splash when I use the stick blender on it. Then I just keep blending until the gravy starts to cool slightly, at which time the gravy color will start to lighten a bit, and the gravy will reach maximum thickening. If it's not thick enough at that point, you can add a little more xanthan (be sure to mix it into a little olive oil first), and blend again.