I'm trying to make soups (e.g. tomato soups, with some veggies, chillies, etc) and would like to make its cost lowest possible.
One problem that I have to solve is choosing the right thickening agent in order to make the soup cheapest possible.
Flour seems a common choice, but there is also xanthan gum. Xanthan gum is more expensive per gram, but looking at the cost per gram is misleading as different amounts in grams are required to thicken a given volume. For example, only a few grams of xanthan gum are required to thicken a serving.
To be more specific, suppose that I have 500ml of hot water that I'd like to thicken, what's the cheapest way to thicken it with a soup-like consistency?
There are many more thickening agents than the two that I have mentioned so far, and this complicates the problem for me as I'm not experienced with thickening agents nor soups. Therefore, experts' opinions here would be really helpful, specially that this question seems not answered here, and my search attempts failed to find any website that answers it.