I have managed to find a place in UK that would do the glass for £230 which appears cheapest so in honesty I don't think it is cost effective unless you are buying in bulk from China with custom panels and making 40 tanks a year in honesty.
I can work them out to cost closer to £100 a tank then which means you could sell them for £220 built to others and make around £100 per tank then. But of course it is the time and effort. It may be worth it if you had enough space to do so.
I mean you can get low iron glass panels pretty cheap. It's about US$8 per m2 and your aquarium is around 1.82m2 so that would be US$16 for all the glass but you need to order 1000m2 in bulk so about 500 aquariums worth
Or you can get the glass for around US$11.50 per m2 so US$23 and you need to order min 100m2 of glass so more like 50 aquariums. Of course there are shipping fees to be added which I can't guess at.
However this is why there are not lots of little independent tank builders knocking 10 tanks a year out as it needs commitment. I did look into it years ago but realised would need around US$50k to set up.
Materials were about 50% with equipment 40% and 10% for first 6 months rental on a unit large enough for the machines.