That sounds really crappy.

I don't have much to say other than read https://www.flyertalk.com/forum/air-...sation-ac.html

You should be eligible for a refund of 75% of the ticket price, though I'd push for the price difference between Standard (or, given you got a middle seat at the gate, Basic) and what you paid, if that's more.

And that's just the refund. I'd definitely push for more. I would have expected them to downgrade J to PY (since it was necessary), and then all the PY pax to Y. In a scenario where J and PY were both full of paid pax (which I think is unlikely), that would only result in 2 J to Y downgrades. And I'd expect that to have a status component, where a 75K (I don't think being on the same PNR as a SE is relevant here) would not be in the bottom two.