That isn't correct.
If the only thing wrong was the outer shell, they can spend the 75 cents and stick on a new one, and sell it as new.
They do reuse NAND, and everything else, which is why they have such a low warranty period compared to new.
They don't do that.
Most refurbs are units that were part of a batch that didn't pass QA. When QA samples bin out, they take the lot and set them aside, for retesting. If they pass, they get the refurb treatment. In all likelihood, these units will be every bit as reliable as units considered "new"
Some will be cosmetic issues. This might be scratches, might be a packaging issue... again, because they don't go straight from the assembly line to the warehouse, they are refurbs.
Finally, you have more problematic units. DOA returns, warranty returns, or binned devices that get resurrected one way or another. These are the refurbs you really don't want, and the lowest quality.
Do they disassemble these units and re-use the chips on systems that still can't be revived?... no, they do not. It would cost more to de-solder the components than to simply replace it with a new unit. These are not socket-mounted chips - they are surface mounted chips, wave-soldered into place. Even with relatively low hazardous materials used in the solder process, it still creates a messy situation. The work to do this is also highly-specialized and unique for every system. That is not how factories are built. Also, have you ever seen the way new chips are supplied to a factory? They come in giant rolls... mounted to tape to be fed into machines. You simply can't remove NAND chips from a circuit board and drop them back into production.
Often times, much of the QA isn't even done on the site of the manufacture, but at another point in the delivery of the product. I've worked with a company that manufactured in China, and shipped to Mexico and Indiana before the product hit the second wave of QA at distribution centers.
Most importantly, "spending 75 cents for a new shell and labeling as new" is most certainly not done, for several big reasons. Liability is the biggest one, but the costs mentioned above is another. More importantly, anybody trying to pass off a product as new that didn't go straight from manufacture to delivery is simply risking too much. Not saying it doesn't happen in sloppier-run factories out of China (thanks to corrupt managers), but most decent companies won't do business with them any more when that happens, and reputation means pretty much the business-death of that contractor.