My Fly IQ was just $30, new, retail. "
This light is bright enough for most any cyclist." Peter White
Gee, I guess since the Dymotec6 and Axa Traction I specified in my post are sidewall dynamos, I must be.
I think my Axa HR Traction was $28, hmm, I seem to remember it was on sale?
Note: This isn't the sidewall dynamo system you ran back in the 60s. Chris Juden, technical officer of the CTC, measured the drag of these modern, quality sidewall dynamos and said it was like riding up a 1 in 500 slope. This isn't what I'd set up for a PBP ride, but my commute isn't such a close run adventure that drag at that level will be a factor. These dynamos have ribbed rubber or plastic drive wheels that mesh into the ribbed dynamo track of the tire and don't slip.
Great, killer, no compromise lighting system that's best for all riders? Duh! Of course not. A valid, useful lighting system that's worth consideration for some riders? Yeah.
I looked up the Fly on Peter White's site, and he's selling them for $70 at least.
Lol, sorry, I see I did miss your mention of Dymotec6 and such.
Personally, I can see a use for someone wanting a cheaper tire sidewall dynamo system, but I have trouble recommending them because they remove a lot of the benefits you get from a dynamo of a always-with-you-no-maintenance-only-drawback-is-initial-cost system. You'll need a front tire that actually has a dynamo track, they may or may not work worse in the rain or inclement weather, they steal one of your two water bottle cages, you have a possible theft problem with the dynamo bottle that you don't have if you lock up your front wheel, I've heard the little wheel that goes around can wear out, and of course they do have more drag than a wheel dynamo. I know you said they don't slip, but I guess I'm not confident they don't slip if it's raining and the tire gets all wet. (No personal experience though).
Modern battery lights are pretty good - I'm having trouble seeing the advantage of a sidewall dynamo system over a battery light, except in some niche cases. The advantage of the hub dynamo is that while it's noticeably more expensive, it's otherwise without drawbacks and it's maintenance and worry free once you have it installed. It doesn't seem like that's true of the sidewall version.