Yes, calculators are made from plastic ^^

[Derek W]

If you look closely at many of the very cheap calculators sold in local discount shops, many still have rubber 'keys'. In fact what appear to be keys are just protrusions from a rubber sheet. I once took apart such a keyboard (after it had failed) and found it was partly made of cardboard. Of course, to sell a scientific calculator for GBP1 (which I had paid for that one) a lot of corners have to be cut.