There are a lot of things one can use before plunking down $35 for
camelia oil.  My choice is $5 a pint mineral oil. Wipe it on, then wipe
with a dry cloth.  The way tubes on my old ShopSmith got this treatment
and sat outside for two years under a box, and two winters didn't put a
speck of rust on it.  It doesn't gum up and get all over your wood used
this way.  It's how I protect the cooper's tools at Sutter's Fort --
they sit out in an open to the elements room 365 days of the year.  They
get the treatment after the first rain, and that takes care of them
until the next year. 

Check out the substitutes for sperm oil.  Nye made one, and there are
others.  Sperm oil was actually a liquid wax rather than an oil --
worked wonderfully.  Jojoba oil is a similar, though vegetable oil/wax. 
It's not cheap, but it is a whole bunch cheaper than camelia oil.  

As for the carnuba wax, were you using a paste or one of the liquid
forms?  The liquid forms just don't do the job of the paste waxes. 
Tried them and found them wanting.  Otherwise, I don't see how moisture
could get under the wax and cause rust. unless it was rubbed down too
heavily and got rubbed off.  Moisture had to be getting to the surface
of the metal somehow. 

What you're describing sounds like flash rust -- the stuff that attacks
metal that has been de-rusted in mere seconds.  Wipe it completely dry,
apply a coat of mineral oil immediately and the problem ought not to
happen.  Mineral oil is a trick I learned from a furniture maker in the
Philippines who keeps his machines in an open shed 200 yards from the
ocean.  No rust.  

Mike in Woodland