Here is something I don't get: while this project is cool, if cost is the goal, once you add monitor, mouse & keyboard, isn't anyone better off with a combo of eBay laptop + Debian?
No, not anyone. Hackers maybe, but not schools. First of all, you won't find 100,000+ cheap-but-quality laptops on ebay, not to mention you'll have to install Debian yourself. Not that it's difficult to install for "us," but these are targeted for school children. The whole point of this project is simplicity.
This was true of computers from the golden age of 80s UK home computers (where the R-Pi founders are coming from). It's not so much true of ebay laptops.
Except back in the day, I had to deal with cassette tapes and only 4K (subsequently upgraded to 16K) of RAM.
30 years ago, I learned code by typing in hundreds of lines of (sometimes buggy) BASIC source code found in print magazines that came out only once a month. Today, all a youngster needs to do is a pull (and in just about any programming language) from Github. Progress is amazing!