So more like this?
Well I guess to get a ball park figure of cost you would need something like this formula:
Case + Monitor/Panel + Lighting (£30/£40) + Controller (£40) + Consumables (£5/£10) + Labour + Shipping
Case - Would need the case to work on to install the panel and lighting so that's why its included.
Monitor/Panel - This would need to be the right size for the window and I think newer screens would provide better transparency and image quality but I've not tested to what extent. Obviously this is a very variable cost depending on the size needed and quality of the panel.
Lighting - This would be LED strips, Molex connectors and diffusers.
Controller - The controller and power boards that come with monitors are usually to big and bulky to be used but of course if possible they will be used but usually a smaller one is needed to mount nicely into the case. (The prices of these can vary quite a lot depending on the panel but this is average) A power adapter is also needed for the LCD. I'm looking into the possibility of connecting the LCD into the PSU. Most monitors require 12v 4a so theoretically it should work.
Consumables - This is things like electrical tape, screws, solder, wires etc
Labour - Whatever you think is reasonable I guess I've not worked out a figure for this
Shipping - I've no idea but I'm an hour above London, so however much it would be to ship a case.