Did some napkin math for fun. There are 12 contacts spaced within 6mm inside a USB-C cable, on each side. Assuming each contact is 0.25mm wide with a 0.25mm gap

Did some napkin math for fun. There are 12 contacts spaced within 6mm inside a USB-C cable, on each side. Assuming each contact is 0.25mm wide with a 0.25mm gap between each, it would only take somewhere around 1000V to simply arc through the air between contacts. And anything over 5 amps is going to start causing resistive heating simply due to how small and thin the wires and contacts are. So maybe, if you built it and tuned it really well, you could push up to around 5kW through a USB-C, with it being on the brink of shorting itself out and/or melting itself.