I ended up getting a reversing ring on eBay for about a fiver when I first started playing around.
Nikon 28-80mm f/3.5-5.6D (no longer made) attached to the body, 58mm filter thread of the reversing ring attached to that, then the 50mm f/1.8D attached to the 52mm filter thread on the other side of the reversing ring.
Great fun to play with, but nowhere near as versatile as a true macro lens.
After that I picked up a Sigma 50mm f/2.8 MF Macro lens a few years ago in the states for only US$50 on eBay (a brand new lens, the Nikon mount version of
this one).
So, "cheap" is a relative term. I don't really shoot much (any) macro any more, I lost my Sigma somewhere in the move from the US to the UK. Still have the reversing ring, and only really brought it out a couple of times to play with it when I first got the D200 (just to see how it compared to using it on the D100).
If the macro calling ever comes to me again, I'll be looking into the Nikon 105, although many people I've spoken to prefer the older non-VR version more than the new VR one (which could be why, last I checked, the non-VR version sells for as much
second hand as the VR one does new).