Doesn't matter if it would cost more. There is a very important principal involved. It needs to be done to change society back to an attitude of paying our own way in the world, unless we genuinely cant.
If we carry on in the current direction of travel we are in deep trouble. The situation is already financially unsustainable, but even the Tories are now in a position where they need to borrow money we shouldn't be borrowing, to give it to people who don't need it, just to try and stop the accusations of being uncaring, or face electoral oblivion.