As John says, if you are paying for maintenance each year, the upgrade cost is much less, almost a manageable amount. So that is what I do. I really think that the SlickEdit web site should point this out better, as quite a few people seem to miss this. Yes, the first year you take a hit as you have to pay the upgrade price, plus the maintenance cost. But after that, each year you only pay the maintenance. As far as I can tell, SlickEdit has a policy of adding at least one major feature each year, to help justify the upgrade. So if you are not on maintenance, it would depend on what that feature was as to whether you consider it worth incrementing the major version number. If it is something you are unlikely to use (eg annotations for me), then you might consider it only a "minor" feature and not worth the increment.
In any case, I am in favour of policies that keep SlickEdit (the company) profitable and in business. I really, really want my editor, as my main tool that I spend all day with, to be properly supported and updated.
BTW SlickEdit 2008 (V13.0.0) does introduce a macro debugger, although work on it is not complete yet and it is a bit buggy. I think they are intending to complete work on it in one of the V13 point releases (V13.0.1?). And they have done one major UI improvement this year - the new options setup with searching, history and many other improvements is great. I popped back into V12 the other day to try something to compare with V13, and I had to change an option. It was horrible - I have become so used to the nice V13 options over the beta period that I really had problems finding the right place for the option. And then I wanted to undo it, and I had to go through the menus again, instead of just going to the history list.