Recommended audience: Startups and large companies who intend to sell software to universities.

Most SAAS is sold on a per-seat basis. But this does not scale to universities, as we have a large number of possible seats, but most of them (students, possibly from different scientific areas) do not use the software, at least for it to be worthwhile.

On the other hand, unpredictable costs (when paying per activity) is also something that does not work, as we need other budget it yearly.

Chris Siebenmann has a really good write up on this issue, which I recommend if you manage or sell to universities.