It wasn't really used enough and it sat in an awkward middle space between luna and sol where either luna high/xhigh or sol med were better cost/perf wise

I'm scared now, my employer only allows Luna and Terra on 5.6. I really hope they will allow Sol then on GPT 6.

Funny thing is they very recently also set a real limit per-user/month, so why even limit the models because theyre "too expensive".

I read that there are rumors that they're getting rid of that tier. No idea where the rumor came from, though. This lends credence to it, I suppose.

Sol price is halved so no need for terra

It probably didn't see that much use, as it struggled to find a niche. If you wanted intelligence tasks, Sol was cheap enough and much smarter. If you wanted performance and cost-effectiveness, Luna was significantly better value while being only a little less intelligent.

Terra ended up just being an awkward middle ground that was not particularly suited for any workload.