Moral Dilemma?

So an interesting question, which I thought would be perfect for this board. This relates to personal responsibility in business dealings.

I sell virtual currency to a game on eBay. Through this auction system, I found a person willing to buy directly, skipping eBay as the intermediary. This person routinely spends $90 a week on currency. At one point they mentioned they would have to buy less currency for a few weeks, so they could buy food.

Now here's the interesting issue. In the game there is a gambling system, which the buyer uses the currency in.

So in my mind, effectively, I'm providing currency to a gambling addict. Now granted they seem to at least prioritize their spending for necessities over pleasure, but do I have a responsibility to stop selling to this person?

As an assumption I've made when analyzing the situation is that this person will buy from someone else, if I don't sell to them.

Comments/opinions?