Does anyone know how much banks used to charge for trading these products before the advent of listed VIX futures more than a decade ago? And how the numbers evolved over the years. I assume it would cost a lot higher than VIX exchange and brokerage fees, but wonder whether it was 10x or 100x the magnitude, and how they adjusted when the listed VIX space became more and more popular. Appreciate any insights or anecdotes, thanks.