Just FYI, before you get all overenthusiastic and waste all your money, that place (Hendane) was selling doujins for probably about twice the actual price, gouging the heck out of people who didn't know any better and making a huge profit off it. Most doujins sell for about 500 to 800 yen in Japan, and 100 yen is about one dollar (well, that's not the exact exchange rate, but it's pretty close and easier to remember), and it's very rare for them to cost more than 1000 yen (or about 10 bucks). That's why it had the "No Refunds" policy stated nice and clear on a sign - otherwise on Days 2 and 3 they'd be mobbed with people who checked the internet and found out how badly they overpaid and wanted their money back.
It's not really an issue if you only bought a couple of doujins, but if you're going to make it a habit, for the love of god don't buy from importers without having any idea what you're doing, because you paid 15-20 dollars for each of those doujins when it ought to have been possible to get them for 5-10 dollars each. Buying direct from Japan is obviously the most cost-effective option, but I don't know if any of the online doujin retailers ship overseas; if not, you'll have to befriend an Japanese otaku and arrange something with him, find an American import shop that DOESN'T overcharge you right up the butt, or fly to Japan and buy the stuff directly.