Wow. Good question!
Basically, I was looking for good prices like you, and it evolved into this...
The enabler was that I had lived in Shenzhen China where all this stuff really comes from, and I have a good friend, Jun Peng who is there now. He was at a point where he wanted to try a different job and we started up this company that you see.. I did the Web / Store stuff... Take a look at
http://arduino-direct.com/sunshop/index.php?l=page_view&p=about_us for the story...
I am an old scrounger / hacker guy and when I saw what prices we could get from the factory or first-level middleman it seemed too good to pass up. I've never been a Business guy but I have tried to get stuff for schools and young people for years (I got 500+ older IBM computers out of IBM and into schools, years ago..).
Also we have put the profit pretty low. Maybe that was a mistake. I hate the idea of increasing that just to look as respectable as Sparkfun or Adafruit..
Also we decided not to make money on shipping, like so many "cheap" Ebay sellers. We put effort into negotiating good shippings costs. And Shenzhen China is the cheapest place to ship from to anywhere in the world...
I'd REALLY appreciate feedback from anyone on how to think about this. We don't have much business yet, and I'd sure like to break even some time

I'm hoping the Starter Sets we have put together will be good for schools at a good price. We are very open to suggestions on those and other products. Right now we can't afford to stock too much, but most things are a short walk from Peng's shared office space. So the "Just In Time" suppliers we read about are real...
Let me know about what your school is doing and looking for. Any suggestions of ways we can connect with more schools / teachers in USA would be appreciated!