Based on some of the feedback I got in this thread so far, plus a private message I got, it seems that Zoe's performance/attitude as a tickler/licker has a lot to do with the clip's success. Very interesting. I thought she had done a good job, but I didn't think it would have that much of an impact.
It seems the position is also a significant factor. It is rather neat, as it offers a very good view of the soles while making them very vulnerable, easily accessible by the tickler. Of course, I didn't invent this particular position. Other producers have done it before. This is just my personal variation of the same theme. But it works quite well, I think.
I'd like to use that position more often, but it might be a bit tricky. Thing is, several of the shoots I've been doing over the last year (pretty much all unreleased material) have been somewhat shorter than many of my past series, with fewer scenes. Quite frankly, that's something I'd like to continue doing in the future (assuming I actually do more shoots). Shorter shoots are easier, less tiring for the models, which is not a bad thing at all. And I've come to realize that doing many scenes isn't all that useful. I mean, most customers can only buy so many clips, so if a series has more clips the tendency is for customers to spread their purchases over more clips, each clip selling fewer copies. What happens most of the time is that one or two of the clips get most of the sales while the rest sell very poorly. So it seems I might as well do fewer scenes.
One problem with this is that fewer scenes means less variety. I have to be very selective when it comes to positions. But there are some basic positions that I feel are almost necessary. Despite the positive feedback I often get about the variety of positions I try to feature in my videos, in practice the ones featuring stocks tend to be the most popular in terms of sales, including very basic stuff like sitting in stocks positions. If I work with a team of two models I often feel compelled to do one such scene for each model. If I do a 4-scene shoot that only leaves two more scenes. And if I use those scenes for positions like the one Alice finds herself in, then I can't do any of the other neat things I can do with other apparatus. It turns into an all-stocks series. Which isn't bad, really, as stocks are always popular. But if does mean less variety. Then again, it seems that when I try to vary things I make fewer sales. And like it or not, sales are fairly important. So I'm not too sure what to do.
Anyway, while I still feel that the physical appearance of the models has a lot to do with how popular they are, it does seem that people can have other, more subtle reasons for favoring some clips over others. I wish I had a better understanding of these reasons, though. There are clips/series that I'm especially pleased with that sell rather poorly, while other clips/series that I don't like quite as much turn out to be significantly more successful. I really don't understand my customers sometimes. Then again, people's tastes vary a lot, and it's impossible to please everyone, so I might as well do what I like and hope for the best.