Mostly it's Twilio costs. I spend an unconscionable amount on my cell phone bill due to e.g. international roaming or international phone calls for sales/support, but that doesn't even crater the approach to the bridge of what Twilio costs me. (And I rush to say "I'm totally fine with that, and wish I spent 100X as much, because to a first approximation that would imply revenues 100X higher than they are currently.")