wow, can't believe I never saw this thread before...
There is no vegemite sold in Chile at all. I know in other countries the embassy/consulate will ship it in, but this is not the case in Chile. On the chilean end, there are no issues bringing vegemite in, but you will need to pack it in your checked luggage as in Australia they will randomly decide that it might be a bomb making substance and since you will undoubtedly have more than 100mL or whatever can fit in the small ziplock bag, you won't be able to bring it, so un-australian
I wouldn't send it in your sea freight, just because as tough as vegemite is, 2 months or more in a sea container in the sun cannot be good for it.
As for getting it sent in, be sure the person sending it ticks "gift" on the parcel, and get them to include the receipt just in case the Chilean Customs pretend not to understand it is a gift. However, as with the sea freight get vegemite sent should only be done by air mail, in which case it is going to be some expensive vegemite. If you are desperate and do go this route, the best way to go is with the tubes (I know, it's not quite the same) or the bucket, if you think that you will get through that amount of vegemite in the time you have until it expires (I am not sure, but I imagine the shelf life is something like 20 years...) as the glass jars add a lot to the weight and of course if they break then there goes your vegemite. If you do get called down to customs to collect it or pay taxes, drop me a PM, been there done that, not as hard as I first thought it might be, despite the fact that my Chilean relocation consultant refused to help me because it would be "near on impossible".
Other tips I have found useful: Make friends with at least one other Aussie family that arrived here before you, because they will a) likely go back to australia for holidays before you and bring you some back, and b) perhaps leave before you at which point if they are good friends you will inherit their pantry stock. Any colleague, visiting Australian business associate, relative, friend or best friend's dog's cousin's owner's auntie who comes in from Australia is here on in obliges to bring you vegemite, make it clear to all...
good luck, hope by now you have found some vegemite somehow...