In other countries formula manufacturers sell cheap and expensive brands. So in a poor village in Indonesia you would likely find only Lactogen, a Nestlé milk sold for about £1 per box.
Go to a city however, and you will find Nestlé NAN as well, at about £5 per tin, and also an array of competing products, all boasting of their antibodies and such like. I'm not sure of the difference, but I suspect the cheapo brand lacks the buzzwords they claim to put in the expensive one (DHA, RHA, bollocks, bollocks, bollocks).
I don't really know if an 'own label' 'extra value' brand would be worse or not, but the reason I think they don't have on is because discounting of baby milk is forbidden, because it's a form of promotion. In the third world there's basically nothing to stop the likes of Nestle pushing people onto formula feeding, causing many many thousands of babies to die each other through poor sterilisation of feeding bottles, and as a result they are able to do what you are suggesting - push cheap milk to the poor (which is obviously profitable at the price, otherwise they wouldn't do it) and then try and persuaded the middle classes that actually their more expensive brand is worth the extra £££ because it will make baby more intelligent/stronger/taller/whatever.
Basically the free market marketing of baby milk demonstrates that price differentiation is used to sell the product to people who would otherwise breast feed (because it's cheaper), so the bottom line is that any discounting is a bad thing.