Didn't you hear about the great teflon shortage of 2008???? :Big Laugh
Seriously though it's probably because they are not a high volume item and where else are you going to get them?
Many years ago my father-in-law sold industrial cleaning equipment and supplies. He had to order a float for a automatic carpet cleaning machine. this part was nothing more than a white pint plastic bottle about 1/3 full of sand with a screw on lid that had a bead chain attached to it. if there was over 27 cents in material cost i'd be surprised. That thing cost over $70! When the manufacturer was questioned about the extremely ridiculous price, they said we rarely ever sell that part so we have to make it worth keeping in stock!
We made one instead for a buck and a half!