I know $400 US is a lot in the developing world particularly if it is borne by individual families. I only gave it as an example and more important I think in a global context or even for wealthy foundations (i.e. Gates) $400 is not really very much. If students do have to pay for credits (and I think institutions will invariably want them to), one part of OER-U student services should be a major effort for endowed scholarships. J.