Adam,  For insurance purposes, the most important thing is
"Replacement Value" as that is what has to happen if your piano(s)
are "lost." Given the current market for almost _all_ pianos, a
replacement piano would likely be rather cheap -- however, you may
have to have one shipped from elsewhere, so there is that expense.

Then there is the condition; if your piano is fully restored, the
replacement is likely not and there is the expense of restoration.
The complete rebuilding by a professional of a grand piano is probably
in the $15K range, and then there is the restoration of the reproducing
mechanism, another around $5K.

It is wisest, though more expensive, to err on the high side, should
the need ever arise to collect.  Of course, you might find an
appropriate replacement for less, but that's basically a "crap shoot."

For example (although not a reproducing piano, still a musical
instrument), our church has a fine 1928 Rueter Pipe organ (3 manuals,
some 33 ranks).  If the church were to sell it for some unfathomable
reason, it would likely get _maybe_ $10K, probably less (down to
"take it out, please!").

However, should something terrible happen and the organ be destroyed
it would take probably $250K to have a replacement built.  Reproducing
pianos are pretty much in the same category, sad to say.

So, stick with replacement value, and have the condition of your
instruments well-documented.

David Dewey