Ahh but you have to have a CC that has paywave (Chase Sapphire and I suspect all of them don't) - maybe no US cards.

There is also a promotion for a 10 myr credit for Uber rides (to and from Sentral) for each one way ticket when you select that option at the machine and pay by cc - BUT the codes don't work and they know it but haven't fixed it, still you pay 50 instead of 55 by paying at the machine (or online).