Unneeded Complexity.

This morning, in between driving around to take number one son to soccer and number one daughter to hockey, and trying to schedule the thee or four other things that have to be done today, I almost ran out of gas. No, I don't mean in some figurative sense, I mean literally. (And I don't mean literally as in not literally, as it often does - see this blog.)

The car was almost empty; I pulled into a gas station (and I do say 'gas', by the way. 'Petrol' makes me wince. As, for that matter, does 'capsicum'.) I put $50 worth in the car and went inside to pay, and that's where it all started to get confusing. I told him "Pump 7" and handed over a $50 note and he said to me that if I bought $5 more I'd get 14c a litre cheaper, or something like that.

This stopped me cold. I don't really have much of a sense for how much a liter of gas costs, so is 14c lot? I asked him, and he said that on my $50 worth, I'd save about $1.50, which to me sounded like something worth investigating. But then he said that this saving only applied if I bought something in the convenience store for $5. Now clearly, if I was already going to buy something in the convenience store that cost $5 or more this is an unqualified good deal - by expressing a preference to buy the $5 item I've already said I'd rather have the item than have the $5, so having the-item-plus-$1.50 rather than $5 is a easy call.

But there was nothing in the shop that I really needed to buy for $5 or more. I could buy something I didn't want for $5, but then does the $1.50 I'd gain from the saving on the gas make up for the negative utility on the thing I wouldn't have bought anyway? Something I wouldn't pay $5 for, but which I'd happily pay $3.50 for? It's not easy.

And then I remembered than the man in line ahead of me had bought one of those protein drinks (and, I couldn't help noticing, a pack of winfield cigarettes - but he was that sort of guy) and I thought that might do it. I'd been to the gym yesterday and I need protein. The protein drinks were $4.65, so all I had to do was to buy something I didn't want at all for 35c and I'd still be up. Some gum or something, I don't know. They'd be paying me to have the gum and I could throw it in the bin as I went out. Gum, of course, being an absolute disgrace.

But this side-deal wasn't as straightforward as that. They were also offering these protein drinks as a deal: you get two for $6. I could, of course, buy 2 for $6, but then I'd probably leave the extra one in the car for a day or too and it'd get a bit too funky to drink. But I'd feel like a chump paying $4.65 for one when I could have had the extra one for only $1.35. I couldn't justify buying a second one... (This happens to me in the supermarket quite often. I need one of something, but they have some deal on where you could also buy 7 for the price of 13 or so and I end up not wanting to buy any. It's my professional training: if you can't tell who the sucker is in a deal, it's you.)

By this point my brain had just completely seized up. I meekly gave the guy $50 and walked out, feeling like I'd been defeated and had left money on the table. I should point out that I have a good undergraduate degree in physics and that for most of my professional life I've been dealing with complex financial structures. I'm not an idiot. I just behave like one.

Postcript: After wrote this, I saw the obvious solution. I was, I think, indifferent between $4.65 and one protein drink. $6 for two protein drinks is really $4.50 for two, so the second one would cost me negative 15c. I could just discard it as I left the shop. Or I could put it in the car on the off-chance that I remembered that it was there and that I needed it. I think though, that at a subconscious level I did evaluate all this, and realised that the extra fuss of having to manage this inventory wasn't worth the 15c I'd gain. I have quite a bit on my plate today anyway.