Just to mention two of your three objections to my comment are in fact objections to ideologies (and are hence the same objection), so we're in agreement there, and third I never said greed was the best of all possible motivations. However, if I may quote the great jester of our time, Terry Pratchett:
"A thumb pressed against two fingers, and the lean figure of Dr Cruces, head tutor, looming over the startled boys.
"We do not murder," he said. It was a soft voice; the doctor never raised his voice, but he had a way of giving it the pitch and spin that could make it be heard through a hurricane.
"We do not execute. We do not massacre. We never, you may be very certain, we never torture. We have no truck with crimes of passion or hatred or pointless gain. We do not do it for a delight in inhumation, or to feed some secret inner need, or for petty advantage, or for some cause or belief; I tell you, gentlemen, that all these reasons are in the highest degree suspect. Look into the face of a man who will kill you for a belief and your nostrils will snuff up the scent of abomination. Hear a speech declaring a holy war and, I assure you, your ears should catch the clink of evil's scales and the dragging of its monstrous tail over the purity of the language.
"No, we do it for the money.
And, because we above all must know the value of a human life, we do it for a great deal of money.
There can be few cleaner motives, so shorn of all pretense.
Nil mortifi, sine lucre. Remember. No killing without payment."
He paused for a moment.
"And always give a receipt," he added. "