Your underlying premise if faulty, as is your model. Uniden built their head from scratch as a separate product, the Whistler remote head is designed from the start as an integral part of the radio. That model is more along the lines of what the Ham radio manufacturers do. Ham radio is a bigger market (maybe) than scanners, but it's not that big a market.
Even factoring in the vocoder for P25, I don't think that the WS1095 as expensive as you project. Keep in mine also that Whistler didn't have to pay the entire R&D costs since GRE had done that and was selling off assets for what they could get.
For those who are looking at RS as a bench mark for prices, I'd say that you should look at their history of high MSRP prices and look at where the company is today. If they even get product, they are going to have a hard time selling it at those prices when there will be vendors with the same product for significantly less.
Simple math. Uniden charges $200 + for its remote head and it can be purchased for $175 to $185. The PSR800 retailed for $499. So add $175 to $200 to the $499. It is highly unlikely Whistler is going to gift the remote head to us. With the design of today's cars there is little room to install scanners so the remote head will be worth the price just to get something mountable up on the face of the dashboard.