Yup... we've helped a lot of people get started with electronics and programming, and had a lot of fun doing it!
We don't make money on parts. We see it as a combination of content (our non-free PDF guide, and our free video tutorials) and support (via e-mail and our forums (http://www.nerdkits.com/forum/)). We wrote the book, which took a lot of time and continues to evolve. And we have to deal with a dozen suppliers, testing the incoming microcontrollers, LCDs, USB cables, etc., picking dozens of different little resistors and LEDs and such into a bag, and assembling the kits and taking them to the post office. Then handle support questions, marketing, and hope to have a little time left in the day to make some progress toward a new video tutorial and/or kit!
And last but not least, I'd like to be able to pay my rent and eat lunch. I think that the HN community understands that profit is not a dirty word, and information is valuable.
More generally, as a business lesson: for a business selling physical goods, even when zero to minimal post-sale support is needed, I believe it's fairly well known that the business must set the retail price at typically 3 to 5 times the cost of the raw materials. This can vary a bit depending on the level of manufacturing/assembly/post-sale action/non-physical value-add needed, but it usually isn't too far from the 3-5x multiplier on either end. Too low and you can't cover costs (labor, marketing, etc), and too high and a competitor is likely to try to eat your lunch.