[wronglyprepaid]

> If gas price doubles does that mean that folks who commute by car go only half way to work or stay at home every other day?

There are a lot of behavior that can be changed, not all of it, but people could skip some trips, maybe only 10% - but it is not 0%.

> If an iPhone costs $10, why would you buy 5 of them?

I have 5 umbrellas but just one body. I sometimes forget it at some place, or misplace it. Nice to have a spare when I need one. I could then leave an iPhone at work for when my battery runs out for example.

> Supply and demand are not infinitely elastic, as some like to think.

Fair enough, my examples were a bit contrived and absurd, but my point is more just that neither supply nor demand is fixed. But yes they are not infinitely elastic, but they are somewhat elastic.