Yes, but that decision in itself doesn't "drive up prices." They offer a product that consumers are willing to pay more for. They aren't a monopoly and don't have pricing power.
But Apple won't sell the OS separately from the hardware. This is bundling/tying and can be grounds for an antitrust suit. The bundling of the OS (which they do have pricing power over) with hardware (which they normally wouldn't) allows them to overcharge for hardware:
And why does it matter that Apple ties the OS to the hardware? Still not illegal because the according to your link, it's illegal if it's a tying of unrelated products. OSX and Mac hardware happen to be very related.
Apple positions itself more as a luxury brand with a somewhat higher price point (arguable) and the consumers are allowed to choose what they want. And they have spoken.