things aren’t priced on cost they are price based on percieved value, so in the case of adding a screen it may cost $10-20 extra to manufacture but because people will want it more the price will go up regardless, but another problem is that adding extras means the company has to create operating systems so the screen works, it’s much easier to create an interface for a computer and let software company’s deal with supporting the hardware.
Although I do think as usb 3.0 gets more common and the hardware and software devs understand how to impliment it we will see a lot of midi controllers with screens displaying information from your software, it never happened with usb 2.0 because it’s not fast enough to send tight images without any lag.
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