That's a bullshit answer. People say that to try and sound high and mighty. This question is a contradiction. Our society is built upon monetary status, it's ingrained in our psyche (the E is not silent).
It is, in my opinion, quite impossible to be rich (Bill Gates rich) and be absolutely miserable. Money can buy you happiness, even if it's not the love of your life. Life isn't about being in love and settling down with that person. Life is about living it the way you want to. Different things interest different people.
If money can't buy you happiness, then I'd like to see you live without it. In all honesty, I find this question insulting to ask, especially at a church. There are very, very poor people that go to church and are miserable. Conversely, there are very, very rich people that go to church and are happy. This kind of question just rubs it in the faces of those that can't afford much and, I believe, would make them even more bitter for the life they've received.
Anyone that chooses 'poor but happy' is lying to themselves. Unless that person lives completely separate from the rest of society and knows not what lifestyle they could have, they would be envious of the people around them.
Sorry, I don't buy this question since both options are fallacies. You can certainly be rich but unhappy, not miserable, but unhappy. This could be due to the choices you've made to get where you are or that you're so rich that you've got nothing left to accomplish. You can also be poor and 'ok' with it, but you'd desire a better lifestyle if you could choose it. No one wants to be poor, if they say they can be truly happy and live on the streets then they're only fooling themselves.