Mark V comes with two pieces of battle-damaged parts, compared to over a dozen interchangeable pieces on the Mark VI, and has no headsculpt. There's absolutely no justification for the V to cost as much as the VI, so Hot Toys must be setting prices based on demand rather than material costs. Meaning, leaving out the headsculpt would do nothing to lower the price of this figure.
And if you want further proof that Hot Toys wouldn't pass the savings on to its customers, they're charging the same for Falconer Predator as they did Berserker, despite Falconer having an unremovable mask.