This article is from the Piano General Topics FAQ, by Isako Hoshino firstname.lastname@example.org with numerous contributions by others.
Generally, an unrestored, average, run-of-the-mill, complete,
70-year-old player is perhaps worth 10% - 20% more than the
same vintage non-player. However, it is always best to have
it professionally appraised. Some players bring very high
values. Player pianos which are grand pianos, original
"nickelodeons" (coin-operated commercial units), and
reproducing players are usually considered high-value player