I was the one that posted the last link for the steam sale... I got it 1/2 of during the 2013 black friday sale, and I've found that it has been well worth the cost. And I had previously used excel, yodlee, and mint, all of which I liked, but not as advantageous as YNAB, IMO.
During the last steam sale, I actually bought a copy for my sister. She's trying it out but hasn't come back to me raving about it.
I have also noted that had I used it for the 30-some day trial, I probably would not have purchased it. It took me a couple months to learn and love it.
I continue to watch for sales because I really think the software is great and would recommend it to anyone trying to improve their finances. And I bought it when we were already at a 50% savings rate, so it can help people in all sorts of financial situations.
If you can't seem to wait for a sale, others have mentioned you can get $6 off using a referral link. There are plenty of them out there. And there's another thread in "reader recommendations" where people post their referral codes ("I used Bob's, here's mine.") It is likely if you post there someone will pick it up and that will be a $6 "rebate" on your purchase.