I am in the market for a Belle or La Scala pair also. Based on what I've found, condition is important, location in country and what era it is from. The last criteria will indicate components including the crossover. Most crossovers will benefit from being rebuilt with new capacitors. Some crossovers are not recommended to be rebuilt as they are wonky (type AB?). If you have to buy a replacement crossover, it is ~$500 which you need to add to the speaker.
As far as value, prices seem to have increased during Covid. One set of Belles in black sold for $1600 on eBay recently. I think $2500 is max for a set in good shape. Again, know what you are getting.....there is never anything wrong with paying extra for really nice condition especially if they will be seen.
La Scala which cost quite a bit less originally then Belle seem to bring only slightly less money as used pieces. A vintage set that had a chunk of wood 4x5 inches on the side missing, sold for $1000 today on CL which I thought was good if you could live with a cabinet with issues. They seem to go for $1500-2500 in general.
Patience is a virtue when shopping I believe.
More experienced members, please correct me as I am new to current market in Klipsch.