@red
Around the time you sold your first round, there were a number of completed PIV listings from $300-$400. Yours were probably worth a bit more considering they were mint/boxed, but I think you priced them fairly considering the usual ebay market. I think one of the reasons people bought them up so quickly is the fact that you're a trusted, no BS seller.
IMHO the $700 PIV listing is one of those oddball things like the $900 scandoubler. (Notice, no scandoubler has ever sold for anywhere near that amount before or since.)