Layering
Layering is the one thing I think many people take for granted on the topic of Breathable waders. Regardless of how good your breathable waders are, they are still only as good as your layering pieces. Jeans, sweat pants, or other non or poor breathable materials will ruin your breathable waders breathability. High quality and properly placed layering pieces, will compliment a good pair of breathables, and make a poor quality breathable wader, or even a non breathable wader a little more comfortable in delaying the sweat build up department. I would expect to spend around $35-65 CDN on a good pair of long johns (IE Polypropolene or Polyester) that fit tight to your skin as your base layer. For Winter fishing, you want to add on top of your base layer a good pair high quality 100 series or 200 series (depending on how cold the conditions are that you are fishing in and the hiking you will do) fleece pants for around $45-80 CDN. Then a good pair of Wool socks to wear under your neoprene stocking foot. In this case I spent the $$$ on the Merino Wool socks by Simms for about $30 CDN. Wool is a quality material in that it still insulates your feet when wet. You can of course be real hardcore and go with Dana's option which will take you to the next level, but the bottom line is it appears as though your layering pieces alone, if you're serious about having a pair of breathable waders, should add up to around an extra $100-200 CDN, or more! When you start going on extended trips you obviously want some back up layering pieces, etc.
This of course isn't including your "uppers" such as a good polyester shirt and a good quality fleece for colder weather which you also wear under your chest high breathables. Your layering pieces eventually total the same price as your waders in all eventuality!
I wore a pair of neoprenes. I then purchased a pair of Simms Guidweights a year and a half ago. Worth the $$$. Haven't tried any other pairs of fake-tex or other breathable waders made from Gore-tex, so I can't compare. Have heard some horror stories from some, so I went with the one with the consisten reputation.