What is the origin of (buying produce) "by the each"?

The same issue appears on a Language Log post where they suggest it is an intra-industry jargon probably derived from similar common expressions such as “by the piece”:

A reddit thread suggests it arose out of intra-industry jargon to distinguish items priced e.g. “$2.99 each” from items priced by the pound or by the quart or what have you,* with additional commenters saying there’s a usage among people who work in warehouses and similar environments who use nominalized “each” contrastively with “case” (so if you need a co-worker to get you a quantity that’s more than 12 cases but less than 13 cases “you might say ‘hey mike, 12 cases 3 eaches.’”

From (riverfronttimes.com/newsblog)

See other usage examples of “prices by the each” here.