Bob,
You can get an entire setup going for far less than that. For instance, a set of camera specific extension tubes for your camera, a good enlarger lens, and a modified lens cap (to mount the enlarger lens) and you're up and running. I consider$150 too much for a 50mm macro lens, regardless of brand. As a side note, I have been shooting scientific material for publications for decades, and so I'm more than familiar with the cost of equipment.