It all depends I use my gold and platinum toners one-shot for consistency, about 50 ml of working solution in an 8x10 tray. You can certainly stretch the solutions for economy.
I keep the gold chloride solution separate from the other solution and mix one shot....but I sometimes keep the used solution if I only do one print and I expect to use it reasonably soon. I also use a flat bottom tray to minimize the amount of toner required. I use it mainly for lith and standard prints, but used to use it for Kalitypes when I did them.