Since no one's answered you yet...

Not that I'm a Solution Developer, but, I do have some answers to some of your questions.
* IBM exams seem to generally be $150 each.
* How? A lot of practice and studying. I found WebSphere Administration to be easy, compared to the developer exam for the same version. Both really could not be accomplished without at least some practice with the product, and quite a bit of reading of the IBM Redbooks.
* Why IBM's programs? At the time, I was working for a company that was an IBM Business Partner and we were getting ready to move from JRun to WebSphere, so it seemed like a good idea at the time. I work for a company that uses iPlanet now, so it doesn't really help.. but some transfers and some doesn't.
My major problem with IBM is the lack of versioning of their certs - your certification with them is only good until the next version of the software comes out. But other than that, it's a solid company that you know is going to be around for a while.
Hope that helps!