Minimal case, plug pack, rollup waterproof keyboard, distro that boots straight to Lisp (CL, DrScheme, whatever) ... and you have a modern equivalent of a C64 for teaching kids to code.
IMO, cost (not counting 3rd world countries) is not the inhibiting factor of why kids don't code. It's motivation. At no point in history has it been easier to learn to code than it is now.
The attraction of Pi isn't in attracting people to learn programming. Simply put, it's an affordable computer in a small form factor that runs Linux.