Just wondering where the expression comes from and who is considered responsible for coining it.
The Online Etymology Dictionary says that "poor man's something" is from 1854.
There is no deep mystery here—nor, I think, any especial history to be uncovered, either. A poor man’s substitute is no more mysterious in meaning or origin than is a rich man’s game, a fat man’s curse, or a short man’s bane.
It was initially meant to reference any item in Poor Richard's Almanack. The publication appeared continually from 1732 to 1758.