Actually, as I understand it, only the Mozilla Foundation is a non-profit entity. The Mozilla Corporation is for-profit and makes considerable amounts of money from search engine (currently Google) sponsorship. Estimates of $5mil for an H.264 licence for Firefox were being thrown around which is feasible for MoCo to pay. However, Firefox is just one product. Mozilla also have a mission to enable downstream projects, and buying a licence for Firefox wouldn’t cover these. They’d then be promoting a format on the web that would hurt long-term dependant projects of theirs; not a feasible solution in their eyes.