There would be a lot of candidate oligopoly markets to attack if Apple got into that business with its war chest. A risk with the DRAM plan is that they could succeed in lowering prices but the costs would be unpredictable and they would then take a very long time to break even, givn the new lower margins, and would have to become a semi house that makes chips for other customers (to get required volume to break even), taking away focus from their consumer product business.