It's not a matter of saving money.
It's what works for each person.
In my case, the climate I live in, Tamiya thinners evaporate in a stupid amount of time, causing 'pebbling' on my models surfaces.
The best solution was the Iso and water mix, even then you have to get it spot on or your in trouble.
Summer aint so bad, but when Winter comes around it's so dry your skin actually cracks on your fingers.
Because of this I have to adjust my mix to contain more water, less Iso, and more retarder.
I really gotta move.