As skiguy mentionned, these are intended to be used with crampons or as camp booties with soles or even to sleep. The sole insulation is one aspect of it but so is the whole front of the foot. When you think about it, we can wear 3 inch thick jackets, but we have half an inch around our toes.
I'm out east, so my playground for these is the presidetials, when it's -20 with >50mph sustained winds. Yes, I'm that type of guy.
I'm thinking I might just end up making my own because nothing in the market does exactly what I want. Ideally I'd want something I can put on and off quickly without removing my crampons. Kinda like a puffy jacket for my feet. For the soles I can always sandwich a high density foam cutout when I put the crampons on.