I don't work on the recommendations team but I feel I can safely say your recommendations are calc'd each day. Unfortunately I can't share more about our recommendation model other than to say its a strong business advantage.
Still sidestepping what the heck all the machines are used for :-) You seem to be hinting that the majority is the recommendations, but even that shouldn't require such large scales. It also doesn't have to be that timely (eg it won't matter that much if the recalculations were once every 23 hours or once every 22). As a user it would be nice if this "strong business advantage" was useful.
