This appears to have been discussed in a round about way in other places, mostly by people who have come up with ways around it, but I feel like it should be mentioned here in the Bugs forum in case it has been missed by TS.
For some reason Note Poles are a unique kind of item. They can't be sold as furniture, because they aren't, and they can't be put into SDBs either, so they can't be sold that way. Seems to me that this is a bug, and should be reported as such. Can't think of any other reason why they would be unique in the game as unsellable items, other than at auctions.
(Hmm, though come to think of it, doors fall into this category too. O.K. there are 2 items that are unsellable except at auctions.)