Yes - I know. It's a deliberate mistake.
Anyway, this is a screenshot from something on TV (via Tony Tooke):
As you can see, this shop offers rabbits eggs for 2/4 (that's two shillings and fourpence) a dozen.
I'm joking, of course, clearly there is no such thing. They can't possibly be selling them because if they were, it would read rabbits' eggs. Of course. I mean, the ability of grocers to use apostrophes appropriately is widely known and noted.