Economics

I am walking down a busy sidewalk and I badly need to pee. I remember that at the end of that narrow alley on the right there is a public toilet. I rush. When I get there I am reminded that to unlock the toilet gate you need a 10 baht coin. I don't have any. There is no one around who can give me change.
My nearly exploding bladder is enhancing my resourcefulness: I have an unexpected idea. I remember seeing a nice lady with a radiant smile squatting on the floor at the alley entrance, begging the passersby for some spare baht. Hadn't I been distracted by my body needs I would have already dropped a coin in her bowl. I grab a 20b note out of my pocket. For most people this note is worth double a 10b coin. And that, of course, includes the lady with the lovely smile. However, I want to pee now, and I need the 10b coin, which I don't currently possess, and that makes it priceless for me, no matter what's worth for you or anyone else.
So I approach the lady waving the note and she responds with that sunrise smile that is definitely not there just because of a 20b worth business opportunity. She surely is as nice as her smile gives away. I try to wear as beaming an expression as hers while I kneel and tell her: "I give you twenty baht, and you give me a ten baht coin, deal?" I hadn't even finished the sentence that she was already rummaging in her pocket looking for a coin. Nice, bright and fast thinking. I wonder how she ended up begging on this sidewalk. She hands me the coin and now her smile is an exploding supernova. I hope that mine can at least partly mirror hers. I can now hurry to the toilet and relieve my good old bladder, companion of so many adventures.
Afterwards I walk past the nice lady again, and she wishes me good luck. I reciprocate. I paid 20b for a 10b coin. Apparently an arithmetic fiasco. But I managed to go to the toilet, tip the lady and get plenty of those reinvigorating smiles. We established an energizing human connection. It was a very profitable business transaction. A rewarding currency speculation.
And that, ladies and gentlemen, pretty much sums up what economics is for me.