How does momentum transfer work when a massive objects collides with a less massive object?

If the collision is elastic, than the kinetic energy and momentum are conserved. This however, would end up to mean, that when a very massive object moving at a very slow speed, hits a very light object, which is at rest, than the light object's final velocity would be much greater than that of the massive object's initial velocity.
I have checked many simulator applets and this holds true. I don't see however how this could be true (besides that the formulas say so).
I mean, it's hard to imagine a truck moving at 1 mph hitting a small marble, causing the marble to fly off at 20 miles per hour.