there's 7 billion people on this planet, and most of them wear at least 1 pair of shoes (so 4 end bits), which means there's about 4x7,000,000,000 pieces of these things.
I'm surprised it's only a 800,000,000/year industry! That means they are able to produce it so cheap (i.e., less than 2c per bit, which is an over-estimate)!
Also, just because an industry brings in lots of revenue doesn’t make it a good industry. I’m sure there’s trillions of dollars exchanging hands in the plastic bag market, but I’m also sure that the margins are getting squeezed so tight that even a PhD in OR couldn’t find a percentage point to optimize. The margin per bag is essentially zero.
that's a good outcome imho (and it's not zero, it's just very low). But this means that the value of the bag and the cost of production is very, very close, meaning it's available to as many people as possible!