Compared to the 'Appel days', FPGA is irrelevant re. cost savings.
Correct; and the FPGA leading into the software system IS a great fit for their TEACHING charter.
I've been watching that for decades: =Indian Simputer failed for 'cultural reasons' - they can't collaborate/share. =MIT's OneLapTopPerChild suffered from the US infinite-frontier/beBIG attitude. People like Wirth, with hardware background would have realised that 3rd-world users haven't got electricity to run current X86 CPUs. OTOH many aspects of OLPC were brilliant. Apparently many in the teaching profession hate the idea of OLPC. Luddites? How much of education is "GOING to school"? OLPC experimenters claim that dumping boxes of OLPC in remote/rural Ethiopia proved that kids could learn how to use them without any human tutors. I wonder how long the electric-accos lasted, with out charging faciliies?
= rPi seems to have succeeded !! It's smaller and less power consuming than WinTel CPU's "air conditioner". I was astounded: having sweated-blood trying to install festival [text to speech] on my PC:Linux:Slakware and failed to compile the source, {C++ users admit that it's a moving target} whereas rPi downloaded and installed it easily.
OTOH, that gives the kiddies the illusion that they "know what they are doing"; which mean rPi is failing as a teaching item. I claim it's absurd to need a decrypted-ethernet-connection to access your rPi-files NEXT-TO your PC.
The rPi-kiddies who take the attitude "the facilities are there, and we know what keys to press", will be un-employable compared to students who learned how transistors & FPGA lead to a final system.