You could have a 1000000x CD-ROM for all I care. Your computer and your processor plays a "huge" factor in importing music times.
My iBook 466 imports at a little more than half the rate of B/s as my Cube 0.5GHz.
The Velocity Engine also plays a part in compressing your audio, as you can tell from the example.
Another factor to consider is how much you are compressing your audio. Compressions down to 192Kbps means a lesser "loss" of data than compression down to 112Kbps, so it takes less time to compress music to 192Kbps than to 112Kbps. Think of it as trying to keep a slice of paper from unfolding after several folds. The longer you work it and hold it down, the more compressed you can keep it.
A third factor to consider would be if you have third party applications running in the background, or if you are playing music simutaneously. Doing so consumes CPU power and lessens the rate of importing.