There's electronics behind those metal contacts. There has to be some transistor system somewhere behind the button or on the motherboard, that registers slight flow of current that happens when your finger touches those metal stripes, and tells the switching electronics to do it's job. All of that is done mechanically in a regular switch, with just making real contact between metal pieces, I'm guessing even if there's only one small IC or a couple of transistors that are being replaced with mechanical parts, it still a dollar cheaper because mechanical buttons must cost nearly nothing. And that translates into millions of dollars savings as that many consoles sell.