My chinchillas all eat apple sticks. I found them to be expensive because at first had to order online. THEN I found three people who had untouched apple trees in their yard. I asked them to cut them only and deliver, I boil and bake, and it is dirt cheap.
Currently, after the loss of my pregnant mother and her two unborn babies, I now only have 8 chins.. soon to be 11 next week, but I can attest that EVERY ONE, which I have them from different lines, some from one place, some from another, etc, not a single ones eats the wood, they LOVE the bark, and they will leave the wood on the pan once they are done. I have found this does wear down the teeth, but I feed them everyday . SOme cannot afford to do this because of the cost or availability.
Some of my customers who have kits from me, their chins LOVE lava bits, lava ledges and perches. I tried the ledges, perches and swinging thing too and they all gnawed them down too.