Plastics are cost effective because they're allowed to be dumped into the environment without any cost, under the guise of fake recycling efforts.

If the plastics industry had to bear the cost of their product, it wouldn't be as cheap.

"For many years, recycling was relatively cheap. North American and European countries were sending millions of tons of recyclables to China, where they were bought at a price that helped offset the cost of local recycling schemes in exporter countries." https://www.rts.com/blog/is-recycling-worth-it/ (randomly picked from search "cost of recycling")