71% of the market of product sold in big-box retail stores, convenience stores and gas stations, as well as online. That market is perhaps 10% (that's being generous) of the overall ecig market, because those tiny things suck.

I'm less worried about metal leeching in higher end mods, the juice doesn't sit for months on end with significant surface area touching metal as the juice is typically vaped in << 24 hours, and the physical designs are quite different.

That said, there is still an element of unknown risk, both with the metals used, as well as the wicking materials, but it seems reasonable to expect high end products where they have better margins and more concern with reputation to put much more emphasis on safety and quality.

EDIT:

I think I will have to eat some crow, after doing some googling it seems there are in fact thorough real studies being performed on real world equipment:

https://ehp.niehs.nih.gov/ehp2175/

I mostly just skimmed this article, figuring out whether these detected levels are beyond what is considered "safe" or how they compare to both regular cigarettes and background environmental exposure I suppose would be nice to know, but based on this article I am going to change my stance to believe that yes, in fact I am exposing myself to heavy metals even when using a high end mod. I think I'm going to do some more research later as I would expect this report would have gotten a fair amount of publicity in the enthusiast community, will be interesting to see how honest their reaction is to this.