I'm not certain but from what I've read, he did manage to get a lawyer to represent him in the trial. For the most part Legal Aid is only given to those who pass a means test and have dire need.
Certainly his need was dire but from what I read he managed to afford a lawyer, thus you could infer that he did not satisfy the means test.
I believe the legal assistance that was denied was his appeal against his convictions saying that he had poor legal representation. It may be poor quality but that does not mean he had no legal assistance. I'll put in a comment made by the High Court upon dismissing his application for appeal: (I'll bolden some key points)
Milat v R [2004] HCA 17; (2004) 205 ALR 338; (2004) 78 ALJR 672 (24 February 2004)
[...]
" 31. When those complaints were made as part of the appeal to the Court of Criminal Appeal, the applicant apparently had the benefit of legal assistance in producing the written submissions. He has had more than one and a half years in which to develop the grounds for special leave that were filed as long ago as June 2002. He has had since 5 September 2002 to reply to the respondent's summary of argument. That summary essentially relies on the judgment of the Court of Criminal Appeal delivered in 1998. The applicant availed himself of the opportunity to answer the respondent's submissions by filing a supplementary summary of argument in January 2003.
32. The applicant's written submissions in this Court contain copious references to legal cases and passages in the judgments in those cases as well as detailed arguments in support of his application. If his written submissions were written for or copied by him, it is unlikely that orally he could improve on them. If he wrote them without substantial assistance, it is not easy to accept that he has left out matters that he would put before the Court orally. Certainly, it is impossible to say in the words of Justice Gaudron that "the issues raised cannot be adequately dealt with by written submissions". Whether or not his written submissions have any merit is for the Full Court hearing the application to decide, but I have no trouble, and I cannot see how the Justices hearing the application will have any trouble, understanding the claims of the applicant.
33. Accordingly, there is no ground for making an order that the applicant be brought to this Court to make oral submissions in support of his appeal.
"
In short, it is my understanding that the High Court felt he evidently didn't need Legal Aid since it appeared he appeared had some.
Of course there's the whole issue of 'trial by media' and the high-profile nature of the crime... Don't take my word for anything on this though; I haven't studied the Milat case at all until I read your post just then.