This argument is moot to say the least.

How are benefits paid?

Do people actually paying them have any choice about subsidizing immigrants?

Are, or are not, violence (taxes) and fraud (counterfeiting, as in inflation) used to make sure the state has enough to spend on immigrants?

That once in a while the imported human material turns out to be a good investment is marginal and inconsequential, what does happen 100% of the time is productive individuals being extorted and defrauded of their wealth for choices they did not make.