I personally wouldn't pay that much for it. I don't know what games cost over there in Australia, though. Plus I don't know anything about the value of the Japanese Taito model. I'm only familiar with the American Midway model. And even at that, I'm more familiar with Space Invaders Deluxe (since I own one).
I can't nail down a good price for you, but this seems quite high. However, the seller mentions there are less than 300 in Australia. SI is much more common here in the US. So I don't know...