[ndsipa_pomu]

That doesn't seem plausible to me, though not because I don't think the upper class would be above such behaviour. If investors try to prop up the price of a company, they'll end up buying more over-priced shares and potentially losing far more money in the long-term, so it's probably only worthwhile if they believe that it's just a short-term blip. Also, the investors that don't believe that it's a sensible long-term bet will be offloading their shares to the people who are willing to pay top price for them, so someone is going to end up holding a lot of expensive stock that's not performing.