That stuff dropped. Materials and undelivered items being manufactured will drop upon explosion.
That structure, and the other large ones probably are worth exploding, but just barely. Each pilot only made about 200M for 1.5h of grinding which isn’t bad, but not much more than the risk-free PvE options on the table.
The medium structures however still aren’t very interesting for a potential garbage collector profession. Perhaps if they are fully fit and undefended so you can do it with a couple ships it would be worth your while, but it still lacks the jackpot feeling of popping POSes had.
Still, I have to say low-powered mode has made them more lucrative to shoot which is good, but TZ tanking does make some just impossible to kill for small groups with real lives. I guess that is fine, but I still think in general they are still too safe for their cost and utility, especially the medium structures. But I am willing to wait some more to see how the Upwell 2.0 changes mix things up before declaring there is still a problem with them.