What kind of question is that? How rude!
Perhaps, but very pertinent to the topic at hand. Many people choose to have a boatload of kids when even a fool can see that it is a highly questionable move financially -- my parents being examples of such fools, as it happens. If you cannot afford the lifestyle, having kids because you want them is no different than buying a plasma TV because you want one. Except in the case of having kids, the parents' financial foolishness may be visited on them in various ways.
I have no problem with people having huge families, but it is a selfish financial choice based on personal desire just like every other such decision. We make our choices, and live with the consequences, and having children is unambiguously a voluntary personal choice. If one chooses to have children, one should not complain to anyone else that they are expensive to maintain -- anyone should have known that going in.
"What kind of question is that? How rude!"
Why is rude to question how many children a person has if they can't provide for them financially?