Is this driftwood for form or function? Do you want a display piece or is it for the Bristlenose tank you were talking about before?
My pieces for the BN tank/s were about $8 each if i remember right. I got these because they were 100 percent safe for aquarium use. One was quite big aswell.
I know people source their own wood sometimes from rivers/lakes (which is supposed to be illegal in Aus

)
Im not totally convinced a eucalypt branch would be safe, I reckon the oils from the wood could be an issue.
Apart from that I have heard boiling wood is a good way to kill any nasties living in and on the branch.
I personally wouldn't use it but I don't have enough info to pursuade you not to.