Mass market, good design methods etc, makes it possible to produce and sell a similar clock at $100-$200 and make money.

But what may make this clock expensive to produce is the white characters. They could have used light bulbs or electroluminicent film, but i nthis case they specifically writes that they are using LEDs.

They did not design it to be cheap, but to have a specific visual look.

They have intentionally targeted people who are willing to buy premium prices for something no one else have. But the customers will only pay the premium prices as long as the neighbour doesn't also has a similar clock. So they do not want to make a lot of money from selling many clocks at a low margin. They want to make the money from selling just a few clocks.

For a school assignment, it is easiest to have diodes premounted in arrays. But the diodes will be close together so you will get a quite small clock without using a large number of arrays. For a real product, you could make a big clock with maybe 4-16 diodes/character. Still only 440-1760 diodes. And massproduced, the cost would not be high at all.

The nice thing with many diodes/character, is that you can avoid a lot of the cost with a high-end diffuser and with screening between the individual characters. You select diodes with a suitable viewing angle that a full-size unbroken diffuser will produce even light behind the character with hardly any light spill to a neighbour character. A white LED is much more expensive than the red or green LED we have been discussing here. But when productifying something, you have a lot more options. Using diodes explicitly intended for lighting an area instead of creating a visible dot, they could be able to greatly reduce the number of diodes/character and get further optimizations when it comes to the need for a diffuser.

What should be noted is that they are making a lot of money from each sold clock. They know that they will sell few clocks. They have made sure that the production cost doesn't eat too much of the sales price. Build 1000 clocks and you would be able to make them for a very affordable price.