RE:HVUthe bid ask is still a floating variable, traders and trading houses can bid ask what ever they want, horizion maintains a base offer that they will move if it gets too out of wack and or there is easy money to be made, then there is the, which month of the vix contracts the fund is actually buying as the options continually roll over and the fund has to manage its risks.
I figure the main function of these etn's is to give the big boys a captive buyer of options they no longer want to have to eat.