The margin, 1.5x, is system income. The fee structure has a fixed component and variable component on the tx size. On those 3x of the gas outbound chain, there is half of that is going to the network and LPs as a "network fee" (1.5x) and the outbound transaction has the other half (1.5x) of that fee to use as gas on the chain, so its up to 1.5x the average current gas to make sure its a fast transaction.