I'm not sure what you think we're using, but please go to ebay and search for "LP156WF1 new" and report back on what prices you find. That's just the screen and you'll find that it alone is around 3.5-5x your quoted price. You'll pay more for one guaranteed for zero stuck pixels which is what we require of our vendors.
Then add to that the cost of a full-custom controller which we developed (and patented), custom cables, custom brackets, custom cut foam and packaging. Add in contract manufacturing, assembly and test, shipping costs and expected losses and you've just covered the cost of goods.
Next take the number of hours you plan to spend on content creation... that's development of the coloring algorithms, tools, and frame-by-frame colorization for your title of choice. Also factor in the value of the library of (currently) 64 color ROMs which can be downloaded for free and changed at any time.
Unfortunately, the costs are quite a bit higher than what you've accounted.
Regarding newer displays, there is a new generation of laptop displays that are a bit more expensive as is the cost of driving them since it needs to be sent using displayport instead of LVDS. The main problem, however isn't the cost. In order to create super-thin screens, the electronics were moved from the rear of the panel to the edge, making the display taller than the generation we continue to use. The taller display won't fit a WPC95 backbox.
We're happy we have the displays we have... there aren't a lot of choices. The previous generation is out of production and we buy up stock whenever we can find it but it's extremely limited.
Regarding your previous comments on LED technology, it's not what's cheapest. It's the only tech available in the form factor (2mm LEDs) we need for pinball. The ghosting has been fixed on the new panels but the lack of diffusion is still there and the LEDs are arranged in a red, green, blue column which gives rise to the separation between red and blue. Hopefully this will improve in the future, and when it does, we'll do our best to incorporate it.