I figured you could probably find rupees in things like treasure chests in dungeons and stuff, but it looks like some are in the overworld, too. Just not by cutting the grass it seems. Neat.
Making money in Breath of the Wild seems like it's not gonna be much different from some other RPGs. In Fantasy Life for example probably the biggest way to earn lots of money is by selling things. That's not the ONLY way of course but it's the way that nets you the most cash. So it's a system...