We decided to not do shirts this year mainly because we cannot offer them at a price point that enough people are willing to buy to even be able to break even on them. One issue is the number you have to buy vs. the number of people who are even interested and the other issue is actually making them look half way decent (which costs money).
We got the blue shirts two years ago (2007 swap). I thought they were really nice (good quality shirts, nice graphic, color shirt). We got them for the people helping run the swap and sold the remainder at the swap for $15 or $20 each. We expected to eat the cost for the swap worker shirts and basically sold the rest at very near cost (I think we were making a dollar or two off of them). We got a lot of feedback saying that was too much for a T-shirt and we assumed that is why we didn't sell many (although I agree it is a decent amount, it is a custom shirt and a fairly nice one at that).
Last year we collected money for shirts from sponsors and c_stowers Dad helped us with printing them (I think it was his Dad). As a way to get sponsors to donate, we put the sponsors on the back and just a little logo on the front-left of the shirt. I think we offered these for <$10 because of the feedback about the expense and because the costs were much lower (between sponsors and having someone we know do the printing). Still, at $10, you're hard pressed to make your money back if you only sell 1/2 of what you order and if you order less you pay more per shirt. Basically, we still ended up having to give away a whole bunch at meetings and if we did recover our costs (I can't remember) it was only because sponsors helped...which means they donated less to the raffle.
Anyway, the logic we used was that it is a bit of added work and (although I love having the shirts) in the past it has actually been an additional expense for the club.
I'd love to hear ideas on how other clubs have done their shirts and how successful they were, but that is why we decided to forgo them this year.