I got my Sigma 105mm macro for about 500$. So it doesn't have to be the worst investment in the wold... Then again, Norway is expensive... About 150$ of that was in taxes...
You might want to look at alternative lenses to just Nikkor or Canon. Some are quite a bit cheaper, yet offer the same qualities as the original lenses for your camera.
You might want to have a look at Sigma, Tamron etc. as well as extention tubes.
Just a small comparison: I was looking for a macro lens, and looked first at Nikkor 105mm micro lens. Here in Norway it would cost about 15000 nok. (About 3000$) Then I looked at Sigmas lens 105mm makro it was about 1/6 of the price. Very similar qualities, so to me as a noob to macro photography it makes little difference. (If I so choose, I can later buy a better lense.)
Just my views on the subject.