With the release of Vocaloid NEO (an upcoming Mac OS X version of Vocaloid), you may very well be able to use Vocaloid on a mac. You'd still need to buy them, though. As far as I know, the confirmed Vocaloid NEO releases so far include VY1V3, VY2V3, Mew, Aoki Lapis, ZOLA PROJECT, Macne Nana, and Hatsune Miku V3 English.
Alternatively, I could install Boot Camp onto my laptop, then install Windows, then buy and install other vocaloids I'm interested in, like Oliver (especially Oliver).
Though that might be more costly than just buying one of the ones you listed.
I need a job, especially with college around the corner.
Oh, and thanks for the help!