You get six sets of legs per pack, and they'll cost about £6.50 a pack. The cost is higher per part than other Kromlech legs sets , but they are for larger models. This should be enough for a standard Terminator box set, with one spare pair for perhaps a Terminator Sorcerer or Lord.
They help convey the size and power of the Terminator. The models stand taller than a normal power armoured marine model, which is what you want for these elite troopers.