I want to make the world's cheapest electric drum kit

each drum is a piece of cardboard, with a layer of tinfoil, and then a layer of plastic wrap - if you then cover the drum sticks in tinfoil as well you can use capacitive coupling to measure hits very roughly

could be even cheaper if you tolerate it being a binary hit/no hit like a rockband drum kit, at that point you can just use a ground strap and run a tiny current through the user to detect hits