Why would anyone pay 300-500 thousand gp for a recipe 4? For recipe 5 I can understand -- icy burst (or anything burst) weapons are rare enough to go on AH for a million or more, -- but recipe 4? Correct me if I am wrong, but I don't think frost weapon is any better than fire weapon -- extra d6 damage, and more creatures are vulnerable to fire than to cold, -- and I see fire weapons on AH only 10-40 thousand gp more than otherwise identical non-fire weapons. Why would anyone pay ten times as much (or 20 times, if you also buy 100 Winter Motes) just to put an extra d6 of cold damage on one weapon?
Or is it just that people PUT recipes 4 on AH for that much and nobody actually buys them? Because I did buy recipe 4 a week ago -- for 30 thousand gp, not 300.