There's some element of survivor's bias here. You only see the items that survived long enough and draw a conclusion on all the products they had then. Also the price/income ratio for any such item might have been quite different.

Beyond this, metal too has serious resource and energy implications. Think mining, smelting, production of the final shape, treatment against rust, paint, transport, etc. There are many steps, many inputs (notably chemicals and energy), and quite some demanding work going into it.

I have no answer to these questions: is it more or less resource efficient to produce 20 plastic can openers or 1 metal can opener? Is it more/less environmentally harmful? Is it more/less socially harmful?