I agree with you that Aikido seminars (and sometimes classes) are sometimes prohibitively expensive. I'm done with high school and done with college, but since my interests will not place me in a high-paying job money will most likely be an issue. (In fact I know that in the six months after college I will earn a collective $3000 while living independantly (of parents) and possibly not having a place to train. I feel your pain.)
Chances are that because the Aikido community works the way it works seminars are not likely to just get cheaper... (that's all I'm going to say about that can of worms...
I do think it's important to examine how much of an issue money is in Aikido. I don't think it's something to a) simply brush aside b) tell individuals that they should just be more comited (sp?). It's a lot more complicated than that.
It would probably be worth it to examine how you spend your time, ask the older students at your dojo (if you trust them) whether they know of any work which would fit with your life, and try to earn the money. If that doesn't work out with your life, you might just have to wait till you can make the money.... or are willing to discuss your situation with the organizer... or are willing to understand that your parents ARE there to support you if they can...