"Let alone" phrase

Question

I'm having trouble understanding the ordering of the phrase "let alone"

For example: "I don't have a dollar let alone a dime" and "I don't have a dime let alone a dollar"

Or (from a similar question on this site): "I wouldn't go near a sting ray let alone pet one" or "I wouldn't pet a sting ray let alone go near one"

To me the last ones are correct, but other people seem to disagree.

In the first one, if you don't have a dollar it's seems you likely you couldn't afford a dime. So the last version would mean I don't have a dime so there's no point even considering a dollar.

And in the second example, it's similar if you wouldn't go near a sting ray then you wouldn't be able to pet it so there's no point in the let alone.

It seems like the "worse" thing should go before the let alone. I have a similar problem with "X never mind Y"

Could someone explain the ordering of these phrases?

Answer 1

The let alone construction has been analyzed in great and precise detail
in a famous paper by Fillmore, Kay, and O'Connor:

"Regularity and Idiomaticity in Grammatical Constructions: The Case of Let Alone",
Language, Vol. 64, No. 3 (1988:501-38).

EDIT: By request. The two clauses have to be on a certain scale of meaning; one of the clauses
must describe a situation that is less on that scale than the other. The lesser clause is usually negative, and comes first. The second clause refers to something higher on the scale than the other.

Thus, *I don't have a dollar, let alone a dime is out because a dollar is higher on the scale.
Ditto *I wouldn't pet a stingray, let alone go near one. In both cases, the other order is OK.
The reasons are all explained in the paper.

EDIT 2: This is also a duplicate of two previous answers I'd already made to this question.

Answer 2

This is OALD's entry for let alone:

let alone used after a statement to emphasize that because the first thing is not true or possible, the next thing cannot be true or possible either There isn't enough room for us, let alone any guests. I didn’t have any clothes, let alone a passport.

"let alone" is usually used after a negative statement. After "let alone" follows a second negative statement that is a step higher on the scale - to say it with John Lawler's words.

http://www.oxfordlearnersdictionaries.com/definition/english/alone?q=alone