I sell a few. More fountain pens than rollerball. Seems like they sell pretty good in tru-stone. They go for $90 - $120 depending on material. I mark up my fountain pens a little more than rollerball, and offer nib choices with upgrade to Heritance nibs.
I found The crystal in the clip can be a good selling point or a negative. Some people like it, some don't. I have been thinking it would be cool to switch the crystal to some other stone to complement whatever the pen is made from.
Anyone with jewelry experience out there know if that would be doable? It would be great to see a tutorial on how to do it.