You can't just multiply out 6 or 7 times the current price to get what it would cost.
As I said, no, you can't, because LCD pricing ramps on a logarithmic scale, not a linear one. Making a display 7 times larger costs
much, much more than 7 times the price.
Based on the numbers you gave - I would ESTIMATE (wild guess here) that the cost would be more between 100-150.
Not even remotely realistic. If it were to launch today, the price would be closer to $400-500.
Scaling up is massively expensive. That's why there are displays at 3.0" at 320ppi, but 3.2" displays cap out at 285ppi, and 3.5" displays previously set the record at ~260ppi. What you can do economically is scale
down.
The early 17" widescreens were regular 19" 4:3 panels shaved down, which is why they were highly economical to buy.
It's also why commercial pricing clusters together on the low end--today a 19" and a 22" monitor could easily be within a few dollars of each other, but you start to push beyond 24" and prices start to skyrocket. The cut down versions are economical versions of the max-size products; not the other way around (i.e., the large products are
not expensive versions of the small one). The larger, more expensive products are more profitable in dollars, but not because they're marked up at a higher percentage--they're priced as low as possible to sell the most they can.
As you said - considerably more... but not to the extreme you outlined.
What I outlined is highly conservative and not extreme in the least.
It's a common mistake, but display products cost
more per unit scaling up, not less. It's not just a matter of adding them together (which would reduce prices because of volume ramping), but doing it in a continuous way, which is much harder and much lower-yielding. The reason glass windows were made in grids of individual lites for so long was because it was a fraction of the price of making a continuous pane the same size. The same principle applies in displays.