It doesn't always take a lot of $ in all cases to come up with something new.

I was looking at Capcom's Kingpin, and thinking about the start of multiball - the balls are locked under the playfield via a ramp which raises to reveal the ball lock (an up/down ramp is not new, but having the ball lock work that way is), and then when multiball starts - the balls are "shot" at the player (in keeping with the theme) from a trap door that is under the playfield, so the balls shoot towards the flippers. Very innovative, but two extremely simple mechanisms accomplish this at little cost.