More likely the reworked nature of the rifle hurt its sale price. The stock is not factory (big issue), neither is the bolt, Rband, FP/follower. The rifle saw extensive work, probably around 1930, likely later.
The price was softer than it should have been though, for one, this is a VERY early 1925, really it falls in the 1924 serial sequence (though few would know and fewer care..), the stock is period replaced and the barrel is factory which is a good thing. Someone got a good deal, but while these rifles are rare, they are only really desirable in original condition. 1924 & 1926 dated are rare, not 1925, they are very numerous (as far as 98b can be classified numerous) compared to every other Simson 98b variation, - they even out number the rather common e-f blocks in actual recordings (e-f blocks are especially common in upper grades, the only relatively "easy" 98b to get nice...)
Most serious type collectors have a Simson/1925, what is hard is finding "ANY" 1924 or 1926, especially in upper grades (almost impossible).