Personally, I think it is a solution in search of a problem. Of course I feel that way about 650B and other items as well.
I have no problem with what he charges.
I find Jan's marketing a bit strange, here is a 120 OLD cassette even though I am a retro grouch and have been touting the greatness of all these old bikes and have never had a problem with freewheels, here is a cassette because secretly I find the new system better and by the way good freewheels are scarce but the cassettes that fit my hubs don't even exist and I will have to build you one.