i think the emergence of the baritone scale 6 string has caused a lot of people to switch to that and dump their uv's. As previously stated, the 777bk is not and never will be a collectors piece do to the large production so people are definately more willing to part with them. Furthermore, 7 string necks are not for everyone and a lot of people sell because they just cant get accustomed to the feel of the neck. Out of all the 7 strings I have played, the UV's neck is definately the widest and thickest.
If you notice, the 777bk does hold its value rather well comparitively speaking. a mint condition one will still fetch around a grand. If they were junk, you'd see a lot lower resale value.
As for construction, my BK is built like a brick sh$thouse. I have been completely happy with it except for one dead spot on my neck....but that stuff happens. QC is never perfect, especially from ibanez. The guard is prone to scratching which would be my only complaint from a design standpoint. But, this is a boutique quality instrument and should not be thrown around. It pains me to see these guitars showing up in classifieds in player condition with all sorts of nicks and dings.
So, to answer your question, theres nothing wrong with the guitar.