billet means that something is machined from a raw piece of something. take a block of 4340 and make a rod or crank from it.
forged is when the metal is shapped by heating.
Cast is molten metal poured into a casting of a praticalar part.
Thier strenght is usually though of in that order as well if the matirials are equal.
they are usually priced in that oder due to te cost of the manufacturing.
think of how much material is wasted when making a billet crankshaft.