In at least one quest for almost all of the different quest givers today, I have been asked to get a super expensive item. And I'm talking 900k-1mil for a couple of them; Mori asked me for an elixir.

Could this be a sneaky way of the site getting in the way of our completing 500,000 quests? Or am I just a conspiracy theorist?

Nah, it's always like this. Mori/Nori generally ask for super expensive items sometimes (elixirs, SubQ, super rares) for whatever reason. Pete is also often overdoing it with his food obsession as well as Carl. So it's not uncommon to actually have bad luck and get asked to fetch an item that's worth 1mil or more. It happens. Not everytime, but it happens.