They're 240 each, and a tyranid player trying to make a strong list is going to max out on these. They're going to fly around the whole game killing most anything you point them at.
I very rarely have to jink a flyrant, since if I end it's movement with it's base on a ruin, or rubble, or forest or whatever I get a cover save anyway.
They're not going to go out of their way to kill a LR. I only said anything in response to the notion that they can't hurt one without landing.
I'm really not sure why soaking whatever's points in shooting for a turn matters. If I can remove your LR whenever I feel the need, and not sacrifice anything in the doing, how is the point cost relevant?