AVR Freaks

Sigh!

It's cheaper because it does not have a DC/DC converter on board to generate its required voltages. A more expensive module does, so the low price is partly offset by the need to add extra components and extra engineering effort. The lack of an on board converter means it is more difficult to change to another display module, if the need arises.

Depending on in what industry you are, component obsolence might be an issue. A more expensive display module might available much longer. If your gadget is some industrial control it might need service or repairs over a period that might span decades. You don't want to tell your customer to ditch your device if it happens to break after one year and you cannot repair it because the display is no longer being manufactured.

So, there's more than just the price ;)

That also has its costs and only feasible if you don't sell too many devices I guess.

Keeping one spare for each gadget you sell, basically means you have to pay for two display modules per device, but just give the customer only one. So effectively you more than doubled the price of a single panel.

Of course you can play with this ratio. But it helps if you select a panel from a reputable manufacturer's official catalogue then one from some obscure web shop that bought a few thousand of them surplus.

I almost sure that every display panel in all mass-produced products is a custom one, not one you can buy from regular distribution.