The Crestron APAD might fit the bill, as it comes in at the cost target you are looking for. It is monochrome and not technically a touchscreen, but it does have a 4-button / scroll wheel interface that could be intuitive, especially if used with a compatible media server or iPod front end. Coming from Crestron, you know that its control capabilities are going to be outstanding. I wouldn't recommend using it with the non-twisted, overall shield cable that you likely have in the walls, though. I will mention, though, that I have seen Crestron keypads operate correctly on such wire, but won't vouch for the quantity and lengths that you may be dealing with.