Yeah, but look at how much parts and the costs associated with each figure to find out why some come with alternated heads in the packaging and some dont.
Figures like Freddy Krueger, 300, Micheal Myers, Ash, ect. Are human sized figures (about 6"- 7" scale) with fairly minimal articulation and deco costs. The Predators are 8" scale figures that require alot more plastic to make, and add to that each piece of armor, each detailing part like the sliding wristblades, dreadlocks, the multi-part face, very extensive articulation and you have double or triple the amount of tooling and molds that need to be dedicated to a single figure.
With these tooling costs, the costs of the actual figure's part molds (which cost a small fortune by themseleves) the increase in required plastic needed, and more complex and intensive assembly and painting process makes the Predator figures far for expensive to produce than the figures that come with alternate heads in the package.
For NECA to make money for making us these more expensive to produce than normal figures, they have to sell as many as they can and get the most use out of the money they invested in the tooling and molds; and to do that they need to sell multiple versions of the same figure. Do I wish I could get all 3 heads in one packaging? Hell yeah! But the costs of business for producing the types of complex figures as the Predators just don't allow it.