The E3 visa requires you to hold at least a Bachelor Degree in a field related to your employment. It's also generally held that this needs to be the equivalent of a US four-year degree, and for many this means that the E-3 would require a lot of work and money to go and get that degree before being able to move – but it's possible you can move without one.
The wording on the actual documentation for the E3 Visa actually says the following in relation to education and degrees:
Possess the necessary academic or other qualifying credentialshttps://www.uscis.gov/working-in-the-united-states/temporary-workers/e-3-specialty-occupation-workers-from-australia
The important part of this quote is the “other qualifying credentials” which implies that there are alternatives to academic qualifications.
What is an equivalency?
In some cases you may be told to seek equivalency from an evaluation company in order to prove that you are trained well enough, or you have enough on-the-job experience to equate to the minimum requirements of the E3 visa.
How is an equivalency calculated based on work experience or training?
The organization you go to will ask you to submit any and all evidence, and ask what exactly you are looking for. In the case of an E3 Visa, you are looking for a Bachelor Degree, and in a field that is related to the jobs you want to apply for.
You will send affadavits, work experience, resumes, websites, and anything else that can support what exactly you've been doing in order to further your professional experience.
As a general rule of thumb, three years of professional work (and in some cases, professional training) equates to one year of education. So in order to get to the four-year Bachelor degree requirement, you will need 12 years of experience to be at the same level.
Who offers equivalency?
I did mine through Silvergate Evaluations who turned out to be great. You send them everything you have, and they will reply with options on who can write your equivalency statement from a University or College in the US.
Prices will vary based on the width of your experience and how many people they need to involve in order to show that your work experience is sufficient.