I totally understand the thing about paper certifications, but honestly Clarion/Clarion West isn't a paper certification.
You don't get in just because you have the money. You send in a submission packet with a certain amount of writing (this varies between plain Clarion and CW but they're both very, very similar to apply to) and in CWs case, an "introduce yourself" kind of bio. They've got readers who evaluate all the applications in what is essentially a slush pile, and they choose who to accept based on those submissions. And in the case of CW, there are scholarships available, as DKT mentions. I assume there are some for Clarion. I applied to both, the year I went, and was accepted to both, but chose CW, so I don't really have a lot of information about how they work. Yeah, it's a hardship to take six weeks off, and even with financial aid not everyone's going to be able to go. But it was amazing. There's really nothing quite like having Connie Willis or Michael Swanwick crit your stories. It was a huge turning point for me, as a writer, and I wrote my first sale there, for my week six story. That would have been "Hesperia and Glory," in fact.
I'm not sure how Clarion handles it, but I know that Clarion West asks us to say in our bios that we're graduates--only asks. There isn't any kind of penalty or complaint if we don't. I do. Not to brag, but to raise awareness of CW. A lot of people think Clarion and Clarion West are the same, when they're actually run by two entirely different organizations. And of course, it's to CW's benefit if more writers know about the workshop and apply, because the bigger the pool of applications, the more likely they are to find a great bunch of people for that year's class. So it's mostly a visibility thing.
Just so you know what goes on, there are 18 students each year. I'm not sure of the exact size of a Clarion class, but I think it's pretty close. Every week you're expected to turn in a story. Every weekday we had class from nine to noon--though often we went till one. Class consisted of whatever the week's instructor wanted to talk about, but mostly it was spent critiquing three or four of the stories turned in that week. After class, we'd pick up the stories for the next day, eat lunch, and then it was free time! Although in that free time we had to read and crit all those stories, and find time to write. We also got an hour one-on-one with that week's instructor. Even without the awesome writers (and in week five, an editor) who taught each week, critting three or four stories a day while also writing your own story--for six weeks straight--is kind of a mindbending experience. I'm told some folks come out of it unable to write another word for a couple of years. Certainly some number of graduates discover they don't really want to be writers as badly as maybe they thought. But IMO, you're hearing over and over that this or that writer went to one of the Clarions because they only accept people with a certain level of promise to begin with, and the very intense workshop experience definitely improves your work. It's hardly a surprise if a lot of the people who go through that are selling fiction.
That said, of course no one needs to go to Clarion or CW to be awesome or sell. Still, if you can do it, it's really awesome.