Why are Ecopia EP20s on back order?

I've never seen OEM tires on back order; anyone knows why they are on back order? I've called up local tire shops and they told me that they are on back order. Tirerack also says they are on back order. I found one dealer that has them, but they were asking $170 installed for one tire, which is ridiculous.

Is anyone also looking for these tires? I just need to replace one tire, which is why I have no choice.