There have been at least a couple Tamron 90's in the Marketplace over the past couple of weeks, in the under $300 range. I love mine, and would never part with it. $300 is usually the starting point for used 100mm AF macro lenses. Sometimes a little less.If you didn't need the AF, there's an SMC Pentax M 100m f/4 in the Marketplace for $120. A great lens that a lot of macro shooters around here swear by. Just a few ideas. If you can afford that Vivitar Series 1, that will be a heckuva lens to add to your bag