I have done a few trades through the classifieds. I know someone that recently bought a partial jar of Souveran through them.
It is a bit harder to send a sample of paste wax than a liquid product. You have to cut some off rather than just pouring it into a bottle. Also Souveran is very expensive. People just arent as likely to cut their $70 wax to send a sample as they are to pour a sample of a $15 polish.