The distinction isn't whether or not you leave the airport. It's whether or not you enter Chile at SCL. To make an international-to-domestic transfer you have to go through immigration there and transfer to the domestic terminal. When you do that, you're officially in Chile and you pay the $140 reciprocity fee. (It's not a visa.) Stop at the fee counter and pay before you line up to get your passport stamped. The immigration officer will look for evidence that you've paid and will send you back to that counter if you haven't paid.