> What about the blue/purple ones? You know, like they had on ancient
> laptop screens?

Passive matrix too. The key difference is there is no electronics 
per-pixel to hold the voltage over the length of the frame, so the LC 
response time must be very slow (much longer than 1 frame) to keep any 
decent contrast. On an active matrix display the pixel electronics 
(transistor + capacitor) can keep the voltage at whatever you last set 
it to for the duration of a frame, so an LC material with very fast 
response can be used (eg 1 or 2 ms is common now in monitors).

> Wow. I didn't expect it to be quite *that* cheap. Even a simple resistor
> costs more than that! (Or maybe it doesn't if you buy a thousand of
> them, IDK.)

If you want 1000 or more you don't buy them from maplin, RS or Farnell. 
Try this:

http://www.aliexpress.com/item/High-quality-character-LCD-7-segment-LCD-module-3-3V-TN-positive-reflective/32293200442.html


cost must be significantly cheaper:

http://www.amazon.co.uk/Sharp-EL-240SAB-Calculator/dp/B0002I8VLU

>> Price is roughly proportional to screen area (the factory doesn't care
>> much how many screens it gets out of each "mother sheet").
>
> Linearly proportional? Or is it "more expensive" to buy really big screens?

Roughly linear - the factory costs to run are mostly independent of how 
small they chop up the glass at the end.

The only complicating factor is yield. If you get a dead pixel within a 
display then you can't sell it at the "dead pixel free" price. Obviously 
if you are making two huge TVs from each sheet of glass it is much more 
likely you have to scrap (or sell at a discount) 50% of the glass area, 
but if you're making 200 mobile phone screens you might only have to 
scrap 2 or 3 of them.

> OK. Again, that's not nearly as much as I thought. Makes me wonder why

> makes it a high-colour touch-screen device...




http://www.gearbest.com/lcd-led-display-module/pp_231779.html

> I imagine touch would be really expensive - but IDK...

The expensive bit in capacitive touch is the controller IC that does all 
the processing. There is also a premium on this because of the IP that 
has gone into the algorithms etc. The physical bit is very cheap, it's 
just another sheet of glass with some quite chunky conductive layers.

> I don't know, but I'm guessing it must be reasonably expensive to

> something?)

A good rule of thumb for medium-volume consumer goods like that is that 
the cost to manufacture is roughly 25%-33% of what you pay. The rest is 
VAT, shipping/logistics, paying for everyone who works in all the 
companies involved, and maybe a little bit of profit for each company 
along the way.

> Sure, but you don't *make* the switch yourself, surely? You buy an
> off-the-shelf microswitch,

Someone else needs to make it though, my point was for their size/weight 
switches are much more expensive than a sheet of bent metal because the 
assembly costs are higher (whoever does it).


> machine is one of those rare objects that contains *metal*. Obviously

> it. IDK, but I doubt it. The machine is also probably quite awkward to
> physically assemble. And they're large and heavy, so storing and
> shipping probably isn't cheap.

You might be interested in something like this, it gives a detailed 
breakdown of the costs of the parts in the latest iPhone (if you didn't 
know this is a very high-end phone that is expected to sell in high 
volumes):

http://www.techinsights.com/teardown.com/apple-iphone-6/

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