Can you get a macro bellows kit for under $100? Of course - anything is possible on the internet.
Pictured above on my Canon EOS 20D is the Spiratone "Rapid-rail" Macrobel Bellows system. I found it online for around $60 last year. For someone who doesn't do much in the way of serious macro photography, it's a great solution for the one or two hours a year I spend photographing flowers and bugs.
The Macrobel systems you're likely to find online will be in all manners of conditions, and I doubt that the lenses included will be standard. The kit I bought came with a mint-condition bellows and three lenses (which are really M42-mount enlarger lenses): a 35mm f3.5, a 75mm f3.5, and a 150mm f4.5. For what I use the system for, the 150mm gets the most use, and I occasionally whip out the 75mm if I'm photographing really tiny spiders. So far I haven't had much luck with the 35mm. It lets in so little light that it's impossible to focus the 35mm lens. The 150mm and 75mm lenses let in enough light to focus.
For $60, the system is impressively sharp. I honestly wasn't expecting much. It requires stopping down on both the 75mm and 150mm lenses, of course, but the end result is definitely good enough for the beginning macro photographer, or someone just looking to shoot a few bugs and flowers once in awhile.
If you're thinking of getting more serious about macro photography, you may want to consider a dedicated autofocus macro lens. Using the Macrobel system, unfortunately, is brutally slow. To shoot a photo of a grasshopper, for example, you must:
- Attach the T-mount adapter to the Macrobel
- Attach Macrobel and T-mount to your SLR
- Attach lens to Macrobel bellows
- With the aperture wide open, extend the bellows to get the image roughly in focus
- Use fine-tuning knob to get image perfectly in focus
- Stop down aperture
- Put finger on shutter release (or remote)
- Watch grasshopper hop off
- Repeat until you actually get a photo
I may be exaggerating, of course, but the process definitely isn't as fast as using a Canon 100mm Macro USM or MP-E 65mm 1-5x Macro lens. Of course, both of those lenses retail for more than $600.
Overall, the Spiratone Macrobel Bellows system is a fun gear bag addition for less-than-serious macro shooters. It can be found mostly on eBay and through some online camera dealers.