Yeah, you could part the whole thing out, but there's so little demand for used parts currently that it's tough to make a business case for it.

New screens are pretty cheap these days; under $40 for a new iPhone 6 screen wholesale currently. Used batteries are worth nothing since new batteries are so cheap (a new 6 battery is less than $10 -- why would you want a used one?) Camera, home button, charge port, prox sensor...even if you put all those together you'd barely have $100 worth of parts, and that's talking about new part prices (wholesale).

New screens are a lot cheaper than $200, which appears to be the price of iCloud locked phone.

"genuine Apple screen" vs. cheap aftermarket knockoff? I have no idea if there's much of a difference.