I have never been keen on taking cards from writers at conferences.
Generally, I like to have the initial contact be the incoming email query. Your contact info is right there: I can add you to my address book with just a few clicks, and cut/paste rather than run the risk of mistakes that come with retyping.
For example, here's an entry in my address book. Yes, I need to remind myself who I am on occasion.
But I've cottoned on to your woodland creature ways (failing to query when asked, doubting my sincerity in asking). So now, sometimes, a FEW times, when I think a project has promise I ask the writer for a card.
So, yes, get business cards, cause as soon as I say "I never ask for cards" I'll want to ask for yours.
BUT, there's one extra thing to do.
I learned this from a VERY savvy writer at the recent Writers Digest conference.
She put three lines outlining the premise of the novel on the back of her card.
She realized, as I now do, I'm more likely to remember your book than your name.
When I sorted through all the stuff I collected at the conference I didn't recognize her name. But I sure as heck remembered the book. I hung on to the card intending to ping and remind her to query. When her query came in (I hadn't gotten around to pinging either!) I recognized her name and her book.
That's one smart cookie.(And yes Colleen, I'm talking about you!)
So, if you're getting cards, don't buy 500. Buy 50 or 100. You'll probably be changing the description of your novel, or even the novel you're describing. Thus you'll be reprinting.
Your cards don't need to be fancy at all.
Your name, your email, your website, maybe your phone number.
AND a description of your book.
This is why you work on getting a good log line. You don't need it in your query, but it's perfect for your biz card.