No, you don't. If it's a split with one other person, you get 2/3 instead of 1/2, that's only 33% more. If it's a split with two other people, that's 2/4 instea

No, you don't. If it's a split with one other person, you get 2/3 instead of 1/2, that's only 33% more. If it's a split with two other people, that's 2/4 instead of 1/3, which is only 50% more. etc. and always less than twice as much. And in all the other cases where it's not a split (either you lose or you win alone), you paid twice as much.