Interesting. Their catalog
http://www.soletech.com/image/soletech_catalogs/soletech_orthopedic_catalog_2010.pdfprovides very little information about what they sell - but they do seem like a good source, though $25 is a lot for that sheet.
EVA, according to
What is the Difference Between EVA and Polyurethane Midsoles?a good read, is used in high end athletic shoes - mostly shoes that are thrown out after 3 - 6 few months, because it is relatively light, but but it has a fair bit of compression set i.e., it changes shape and looses its cushioning and bounce. Extreme ultralight is a lost cause in figure skates - maybe I'd rather go for polyurethane's durability.
My attempt (trial in athletic shoes, heavily used for fitness training) to use the cheap stuff (the Walmart/Ozark Trail camping mat) has so far been partially successful. It now just feels normal as insoles go - but it is no longer particularly bouncy. I think one wants something that is somewhat bouncy, for jumping. But it feels a lot more durable than the carpet padding, which wasn't bouncy at all. It's certainly a cheap way to get a lot of bulk foam, without having to buy hundreds of square yards. All these camping pads are is one big piece of foam, cut to a specific rectangular size (about 8 ounces of it; ultralight backpacking fanatics cut it down further, to the size and shape of their bodies to make it even lighter), so it isn't surprising it's cheap.
I contacted Therm-a-Rest about their blue foam camping pad, which was on clearance from REI. Their pad is mostly polyethylene ("This material is mostly polyethylene with a small component, less than 10 percent, EVA. Probably between 4 and 9%."), which, according to various sources, has more compression set than the polyolefin" in the cheaper Walmart/Ozark Trail mat. But I was very pleased one of their tech guys,
James Nakagami, was willing to have an extended discussion about it.
He knew it wasn't his field, so he recommended Superfeet, which are expensive and didn't work out so well for me - though, to be honest, that was before I realized you can completely reshape insoles to do what you want. I've been making insoles for myself for a long time, and have mostly been happier than with the commercial products.
I wonder how well cork works - how well it cushions, how bouncy it is, how durable it is... It's been used a lot in for high end ski boots. Partly because it heat molds to the shape of the foot fairly easily (in other words, when you heat it, it has a lot of compression set.), a lot of ski stores do that.