You are correct that there are fake Casios out there. Not only Casios, i've seen rep Ice Watches and rep Daniel Wellington pieces that retailed for $2, that's 5% of the $40 gen.

If there is a point below after which repping isn't financially viable, it's buried deep down in the abyss. Actually, i think it's even below the $2 threshold set by those DW watches that you can get on Ali.