Some people actually act offended when they see that a developer, whether it's a big-time company, or just some guy programming in his bedroom, puts a small price on something they spend their time working on. They will rant and rave of how great the product is, but when they see a price tag, even it's just a few dollars, they scoff at the idea of having to pay and then proceed to say how "worthless" it is.
It's a matter of expectation. Take EditPad, for example. I downloaded the free EditPadLite when I got tired of Notepad. It's a decent text editor. EditPadPro has more features, but a price tag. I don't care about those features (if I want to edit specialized files, I have programs I paid for that do them better than EPP). Then I found NotePad2. It has many of the features of EPP. But it's free
Thus, the expected value of EditPadPro is nil. When you can get 90% of the features of something for free somewhere else, then version that have a cost are meaningless.
Contrast this with the oXygenXML editor. This is the best XML editing tool possibly in this galaxy. It also has a substantial dollar value attached to it. But no free tool comes anywhere close to having the featureset (Emacs with proper add-ons can come semi-close, but Emacs has the worst user interface this side of VI). So the expected value of the product is substantial.
When you can get something great for free, and you've been able to do it for years, you get used to it. You expect it. And thus, you are disappointed when it is no longer free. Indeed, it can feel very much like a bait-and-switch when it happens. But if it's always cost money for something, then people don't have a problem with it continuing to cost money.