Keep in mind, even the major brands are re-branding flash they buy from other manufacturers. So e.g. maybe Sandisk manufactures the high-end 64GB cards themselves using an advanced process, but they purchase the 4GB cards from some shitty manufacturer using a decade-old process.
It doesn't work like that. The model your parent comment is discussing goes like this:
1. Sandisk decides how much to charge for 64GB cards.
2. That price creates a certain level of demand for 64GB cards.
3. Sandisk manufactures many, many more 64GB cards than it can sell at the price it established in step (1).
4. Sandisk downgrades the surplus cards to lower capacity so it can still sell them without eating into 64GB card profits.
What you appear to be missing is that if you have extra 64GB cards, you can't necessarily sell them without lowering the price of 64GB cards across the board, leaving you having sold more cards for less money. So that "profit they could have made" that you refer to is illusory.
NO ONE disables good flash memory without reason.
But if production costs are (even almost) the same for a 4GB card and 64GB card, why would you ever produce a 4GB card? A 64GB card can be sold as 1 through 64GB -- rather than collect dust as a 64GB card if there is higher demand for cheaper cards.
Now, I'm not certain that prices are similar, but it seems reasonable that if you already have quality control and precision enough to make 64 GB cards, it would be cheaper to just make one type of card, than different types.
right?
If this were true, it would be hard to buy SD cards. But it isn't?
Now you see undersupply?
I speculate that as manufacturing processes have gotten better, several segments of the industry simply continue to follow the old pattern of lower performance/lower price (GBs of flash, frequency of processors) from processes that did produce "quantifiable" low yields (eg: disabled core that didn't pass q/a, unreliable flash etc).
As for re-enabling flash on lower capacity cards, I remember seeing a reference to some people being able to flash/reprogram/reconfigure SSD drives for higher capacity -- not sure about sdcards. Also not sure if that was just to alter the reported capacity, or actually enabled more flash on the drive -- I can't find the article right now.
Given stuff like:
http://www.bunniestudios.com/blog/?p=3554
It doesn't seem too far fetched that it's possible.