Olives seem to occupy a huge Mediterranean trading niche from the Mycenaeans onward. Why? Aren't olives rather labor intensive to process? If it's due to the oil - was it because of a fat lack in the Mediterranean diet? Some kind of industry? It just seems too ubiquitous to just be another commodity, like grain or wine. How much olive oil was being consumed per household?
In the ancient mediterrannean, olives were the sole oil crop. If you wanted a cheap oil for cooking or illumination, you use olive oil. Olives are not especially labor intensive to process, compared to other food and non-food crops -- they are pressed using a series of heavy stones, then a mesh or latticework filter was used to remove large chucks of pits and other woody debris. Furthermore, compared to many other crops, growing olives requires relatively little rainfall, and olive trees will thrive in rocky alkaline soils and on hill-slopes, real estate than cannot be easily used for growing grain.
Also, there have been some threads in the past on this very topic, which I so rudely summarized in my reply:
https://www.reddit.com/r/AskHistorians/comments/1kjgqm/why_was_olive_oil_such_a_big_deal_to_ancient/
https://www.reddit.com/r/AskHistorians/comments/3o38et/what_drove_the_demand_for_olive_oil_in_the/
https://www.reddit.com/r/AskHistorians/comments/1kn9do/how_long_could_olive_oil_be_stored_for_in/