Intuit offering an upgrade for $10 more than Amazon charges for a Full version is *not* a good deal.
For someone who doesn't have an older version, yes, I agree with you. But if you have the previous year's version, considering how few and how minor the improvements are, I consider it to be *way* too expensive. Very few people would find it worthwhile.
I also usually upgrade every two years, but sometimes I mistakenly think the new version is worth the money and upgrade every year. I'm running 2012 now, so I'm in no hurry to get 2013. But I'll wait for Turbo Tax to be released and will likely buy a package of the two of them at a good price.