Most have a round cross section, though a few are made with an oval cross, the latter breed being slightly flattened and almond-shaped. Despite their popularity, briolettes are not usually mass-produced. According to Green, Berry, and others, discount stores do not often trade in them, and many jewelry stores won't sell them unless they employ a custom jeweler on site. Briolettes are unique, and at the moment quite fashionable. They were even more so in the past, but with the slowing economy the demand is slipping for them.
Economies fluctuate, of course, and so do fashions.
What is popular today may not be tomorrow. Then all of a sudden yesterday's fashions are popular again. What comes around goes around.