Hello, author here. Happy to answer any questions! My apologies for the downtime, I wasn't expecting much traffic today since I submitted the post to HN yesterday but I've started scaling my server now!
Even your calculations are way too optimistic.
Giving it little thought, I can say that NYC would have at best 10k sales of this item. In total... including any knockoffs.
The product may have scaled to be able to sell to London, Paris, Tokyo, Soul, Beijing, Shanghai, Hong Kong and Singapore. But this is the total addressable market for this item.
Let's say you have 2 engineers in US working on this full time - that's 500k in salaries(that includes all associated staff).
In NYC you would be able to charge $300, but no other major metro area has that kind of disposable income. In London the max price would be $170, Paris and others - $150... And boom, you can't even make a product to cover development costs.(not to mention any operating costs)
Cool art project and commercial viability clash perfectly here. This item is at best - an art piece, that should cost as such($3000+).