Why do yahama use plastic key boards when their products are so expensive?

I have had my Yamaha CVP 203 broken keys fixed four times at great expense and once again I need four more keys replacing. This is diagraceful. Clearly yamaha are over rated and I do not recomend anyone spending their hard earned mony on yamaha thrash. For the price we are asked to pay for yahama digital pianos I expect much better materials to be used insted of plastic. Yahama! if you read this complaint then improve your products and give us the quality we in England expect!