We did that pop up craft/vendor sale today for my wife's sewing business. It wasn't fantastic but wasn't a total loss either. She made a few sales and got one custom order for a bag. Several people took her card and showed interest in some of her custom items so you never know if that might generate a purchase in the future.
We signed up to do it again on March 20. Hopefully the weather will be better then and there will be more customer traffic. These pop up events are relatively new and still building their reputation. Another month or so and hopefully more people know about it and come out regularly to check it out.