>>>If I can buy a case of beer for $20 in the US or go across the border and get a case of the same beer for $18, what does that mean?
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>>It means you didn't say 20 USD here vs 18 USD in Canada - you say dollars and dollars, but fail to say which dollars. So it means I have no data - i.e. have data but no metadata, don't know what the data represent. Which again shows you didn't travel much abroad, or else you'd know that mentioning prices without being precise about the units will get you into anything between a confusion and trouble, depending on the exchange rate.
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>Yeah, should have worded the tile differently, but the example remains true.

Truth wasn't under doubt here - it was the precision of expression, specially when you're talking about two countries whose currencies share the name but not the identity, i.e. CAD is not the same animal as USD.

You should have seen my dad thirty or forty years ago, when we traveled most of the eastern Europe - we'd just stop in front of a shop window and say "wonder how much would that ... be" and he'd churn the conversion off the top of his head in a second. And he did that in four countries in a row, each with a different currency. Took me a while to master the technique, which is basically a turbo guesstimate on where does the odd jagged number fit between two that you can easily calculate (i.e. if you need to multiply 3245 with 34.4, you multiply it by three, add 10% and then round it up a bit; to multiply with 7.2 you multiply with seven, then with eight, then take about a fifth of the difference and add to the first - all of it with only a couple of significant digits, estimate the rest - works like magic).

Imagine the days before the Euro, living in a small country like Belgium - within an hour's ride, you get into one of three areas where some other currency is used... and they speak a different language. You'd get used to it, no problem, but just try to imagine how it'd be.