I don't know why you decided to contradict yourself. You say they don't pay taxes and then the taxes they pay don't offset the benefits they receive which are two completely different things. Clearly they are paying taxes and a redistribution scheme takes money from the top income and transfers it to lower income by definition. There is nothing surprising about this.

You're also forgetting that those workers exist. Beyond taxes the benefit of workers is also in the products and services they provide. When you're a retiree you still need someone to stock shelves in the supermarkets and sit in front of the cash register or someone to work on a farm and pick up the harvest.