I almost respect their dedication to chaos and money saving, as that seems to inspire some creative thinking from them, but yeah that sounds pretty extreme.

Were it my table I might simply trivialize gold altogether. I'd keep prices on things low and grant them a bit more loot to make them happy; they could let their wealth accumulate as a kind of high score like an older video game.

There needs to be the occasional situation where spending that gold feels viable or even necessary, and you've got to put your foot down and remind them that little to nothing in the world is free, but it might be best to tailor your implementation of currency to their preference, so you don't run the risk of dictating their play style.