I can understand how it may seem that way when a plastic takeaway box costs $0.1, why should this cost any more... The article's cost assumption is just based

I can understand how it may seem that way when a plastic takeaway box costs $0.1, why should this cost any more... The article's cost assumption is just based on the cost of the raw plastic material, which is hilarious (3D printer time doesn't really come free). But in more realistic mass production you'd make a mold, and the cost of the mold is dependent on how many "shots" you want to get out of it. Making plastic parts at the cost of takeaway boxes requires expensive high-volume molds. At 10k volume you'd be happy to get the box for $1 including amortised mold cost (though in reality the box could be much smaller, reducing mold & material costs some).