I think the Aronath is a bit special since it was a piece that were made during the LOTR days but never released
in it's original form, a modified version became the book-ends in the FOTR extended DVD edition. When it finally
was released in it's original form to start off Weta's return to LOTR collectibles in 2010 it had an edition size of
only 500 pieces and sold out rather quick. I assume many of the pieces were bought by collectors of the older
statues/environments and stays in their collections.
Some of the statues "back in the day", like the Cave Troll, Witch-King in true form and especially the original
Balrog got a very high second hand prices after they were sold out. The Balrog sold for retail at $300 and
according to Toytracker it sold in the neighbourhood of $2500-$3500, a few times even slightly higher!, in
2005. After the LOTR movies ended and the interest faded somewhat the prices came down a bit but a few
of the older pieces still maintain a high second hand value. You can have a look on the Toytracker site, even
if it's a little misleading for some statues since prices for newer statues, like Bilbo, has become intermingled
with the older statues with the same name.
Auction Tracking and Collection Management for Film and Comic Memorabilia