"Exploded" is a metaphor. "Go up in value" is not. So, I'm comfortable with the relative accuracies there. "Doubled" or "tripled," if true, would obviously be a lot more accurate than either. Ninety-nine percent of the world has never heard of Fantastic Four #48.
I, for one, would not have to think that the vast, vast majority of purchases are speculation driven, given the meager polling that's been done on this issue. Does it make sense to point out reasons to suspect speculative motives? Sure. We just don't have the facts to draw conclusions.