Here's the rub (and the danger of SAAS). This falls into some heavy psychology so:
tl;dr you're a human being, you're going to choose what you think is a deal but you aren't going to jump through the hoops to get it, you're going to be screwed.

Here's the science:
So taking a simple example. Joe is a damned fine php/javascript developer. He is in a decent demand as a private contractor. Joe LOVES Jetbrains' tools. He uses youtrack to keep his work in line, he uses PHPStorm as his php ide and WebStorm for his javascript and has TeamCity handling CI.

He gets the news that this is coming in and sees the fanfare and the pricetag and is like "wow! way to go jetbrains! $19.90 a month for ALL of your tools or $199 a year?! I mean that's only slightly more than what I'm paying now for my renewals at the yearly rate and I'd get all of their tools...." but Joe doesn't have time to look into it Joe is a busy contractor, work is coming in fast and furious now and besides, his current license doesn't expire until March. Nothing to see here.

Well winter comes and work slows down as it does during the holidays, except this year it doesn't pick up in the spring. It's dead slow. It's the end of February and Joe's considering getting well...a "Joe Job" when the phone rings and it's a client with a fat contract to put him back on track. But the project needs PHP version 5.whatever-the-hell-the-new-hotness-is and PHPStorm only supports up to 5.old-and-busted. Time to download the updates! Oh crap, his license is expired. Wait didn't he see something a while back about nw licensing options. He certainly doesn't have the $178 dollars it's gonna cost him to upgrade PHPStorm and WebStorm right now and he REALLY needs it to do this project that's going to get him back on track. So he checks the pricing. Hrmmm $24.90.....wasn't it $19.90 when I looked before. Oh, it was a promotional. Damn. Joe doesn't have $24.90 either, maybe he can just buy the updates for the products he uses. Oh look it's only $9.90 for phpstorm and $9.90 for webstorm for the month...oh wow but together it's MORE than he used to pay for his renewals! What's going on JetBrains?! He used to only pay $178 a year to renew both products but now it's $198. Well that's a no go. So Joe decides to do the month to month thing and when the check clears from this job he'll just update to the full year! So 20 bucks and a couple downloads later Joe is in business. Wow this new version is great! The Jetbrains devs still have their stuff together even if their business people don't. He knocks the project out of the park. Well a month passes and Joe sees another ding on his credit card for jetbrains....oh yeah he should switch that subscription. He'll get to it later. Well a year goes buy. Another winter and another slow spring and another big project to bail Joe out. Only this time Joe doesn't have the 20 bucks to renew that month. Well no big deal Joe can just fire it up and use the old version he doesn't need the latest and greatest. Except, Joe can't. The subscription has expired and so has the tool. And so like a shallow friend when the money ran out so did Jetbrains and left Joe without the tools he needs. All told over the year, Joe spent $237 dollars on a product he used to spend only $178 and had nothing to show for it.

I realize there are some things Joe could have done better, bad business practice etc. but this could very well happen and does all to often. Sure there are alternatives but the goal of a good business isn't supposed to be to force you into the arms of an alternative...you might get comfortable there.