well, I may not be some big city lawyer... (another words I don't know jack) but
all depends on the VIX FUTURES, and where they were pointing at those other times.
and VXX is ratiod between 2 months, (current month and following month) at different percentages throughout the month.
so kinda hard to directly compare TVIX price, with S&P price, and blame it all on decay, contango whatever.
but, I agree, TVIX blows lol :)