Yes he is, and yes they are. You keep trumpsplaining his pronouncements as just so much huckster hyperbole, but I guarantee that neither Trump nor 90% of the MAGA base really know what a 500% price reduction would mean in practice.

They might not know how to translate a 500% reduction into actual values, but they are well aware that Trump isn't proposing to start paying people to acquire medications. The same is true of Trump.

Both speaker and audience know full well that the "500%" figure was chosen to be absurdly, impossibly high because it is being used figuratively and hyperbolically in that context. Indeed, intentionally. So they're reaction to critiques like this will be exactly the same reaction that you or I would have if some pedant were to say, "Actually, no one can go out there and give 110%, so clearly coach has no idea how percentages work." Or, again, to observe that the neighborhood cafe almost doesn't have the "World's Friendliest Staff." Or whatever phrase is clearly being uttered and understood as figurative.