If you want to get rid of these tubes in a hurry, you could donate them to NAR for the purpose of distributing them to NAR sections conducting 'make-n-take' sessions (and you could take a tax write-off for the full normal retail value)
If you want to try another auction route, you will have a rather different audience if you post an auction on ROL
If you want to set a fixed price, you could post a note here on TRF
If you want to boost business, you could advertise that you are throwing in one of these old BTs for every $10? $20? of regular merchandise ordered