Do tribute on Dimhammer at least. I use the HP and AC tributes (but my war is AC gimped as you know). I used to use a good site for tribute values but I think it's gone now. I did find this, though:
I used to do well buying the various Compound Bows in bazaar. Used to be able to buy them for 20-25K and tribute from 40-50K. They aren't so easy to find at a good price now, though. I can't recall the max amount of tribute you can purchase at once but it's at or over 100K.