I don't think production quality is the only reason. Sometime it's cheaper to design one product and sell it as multiple products to capture more value. For example, some people are willing to pay 1k for a graphics card while others are only willing to pay 300. So you sell the same graphics card to both groups but for one you artificially lower it's capability. This allows you to capitalize on the market a lot more efficiently than selling your product either at a low price or a high price.