We can find implicature all around us, from how we use sarcasm, to how we use innuendo. I think that some comparisons can communicate something else, too. So, say, for example, that I say:
Today's as hot as hell.
We take the second comparator as a given (exceedingly and unrelentlingly hot) and use that given to determine something about the first (that it is very, very hot). The implicature of this is that you know that hell is very, very hot, and that then gives us information about today. This works with lots of them:
She is as hot as Georgia asphalt
As strong as a bull
Drunk as a lord
I'm not as drunk as you think I am
So the lesson: our defaults are to take the second comparator as the given. You have to be committed to the obviousness of the heat of GA asphalt and the strength of bulls. Lords are drunk, and it's clear you must think I am very, very drunk. The second comparator can't be even in question for the analogy to be successfully communicative. (Or, at least, it is communicated as being taken as beyond question.) Notice how one of the two following comparisons is the funnier 'your momma' joke than the other:
Your momma is as fat as Jupiter
Jupiter is as fat as your momma
The second, because your momma's fatness is taken as the base comparator for Jupiter, not the other way around. That's funny… in a 'your momma' joke sort of way. Here's where the interpretive lesson gets weird. I bought some bargain basement cat litter at the corner market, and it had the following comparison on the back:
For those of you who are as passionate about your pets as you are about price.
Isn't the implicature of this comparison that whoever buys this cat litter is someone who is passionate about price? Isn't this an overstatement? Shouldn't it be realistic about price? Moreover, isn't this a questionable thought? I'm not passionate about price at all, but I love my cats. So shouldn't the comparators be switched? I think it's a more obvious commitment that we're passionate about the pets. I don't buy cheap cat litter because I have a passion for saving money, but rather, I have a passion for beer, travel, nice things, cats, and so on. So I buy cheap cat litter to fit the budget. That's not price-passion. That's other-stuff-passion. Or, perhaps, I'm not the target market — I had no idea Ebenezer Scrooge was a cat-owner.