The question, I guess, is if the customer is fountain pen 'saavy'. The quality of the fountain pen is judged by the nib. Basically, the inexpensive nibs are made of steel and are from Japan. The higher quality nibs are made from gold and may be plated with platinum, etc., are made in Germany and are obviously more expensive. My suggestion to you would be to gauge your customer's interest. If he doesn't really know pens, then you could order a nice kit from craft supplies (
http://www.woodturnerscatalog.com)...their kits seem to have a good reputation for having a half way decent steel nib. I have read many accounts of people who are somewhat pen saavy being quite happy with their nibs.
Now, if your client wants to tack on an extra $80-100, there are opportunities to upgrade these pens with a gold nib that is as nice as anything else on the market. I'm not a fountain pen expert, but have sold a few fountain pens, a few of which included the 18 karat gold nib. I would be willing to bet that the average person would be quite happy with the csusa nib unless they are a collector. If they are a collector, you seem to know it right away as they won't deal with someone who isn't confident in their knowledge on the topic.
Finally, I would recommend supplying some ink with your pen. It is amazing how much inks differ and give you different writing experience. My experience has soley been with Private Reserve. Even within that brand, you will find some inks that flow nicely and others that are quite a pain to get to flow through the nib. Given that the pen writes through capillary action, the viscosity of the ink is important and that varies just from color to color within the same brand. I have found that tanzinite is one of the favorite colors in Private Reserve because of the flow/viscosity. My experience has black cherry to flow very similarly and I prefer the color. The other thing I found is that I like DC blue ...something..can't recall off hand. It flows much more freely than the other colors (a bit more water-ey) so you can write more quickly with it. So, black cherry is my fav, but would go to DC Blue if I will be more in notetaking mode and needing to write more quickly.
Hope that helps!
Regards,
Chris