Over the years I have observed a big difference between Japan and New Zealand to do with the handling of money. There's a lot more to it than meets the eye - a lot of unwritten rules.
My friends and I have a few arrangements which could easily be traded on word alone. They babysit for me, I teach them or their kids English. I'd be happy to say "You do this for me, I'll do that for you" but they seem more comfortable paying cash. Everything is all squared away each time.
The money is rarely given over directly instead it is put in an envelope. Luckily envelopes are never in low supply. We all have these leftover ones from the New Year's exchange of money o-toshidama. We've worked out a system where we pass these cute envelopes back and forth to each other. It's strange but I've gotten used to it now.