Some forum posts indicate that cored beads sell better that uncored. That finding parallels our sales at Alaska Boro Beads. These just look finished. With that extra touch of ‘special’.
Producing a cored bead is not overly complicated. The ‘danger’ part is that it is another process that could damage an otherwise good looking bead. i.e. in some cases that pretty bead ends up being cracked and thus non saleable or just poorly cored.
There are a number of tools available for this process. The simplest using a set of domed punches that are referred to as dapping punches. 
These are readily available from any number of net suppliers.
One such set from Harbor Freight is inexpensive, but also did not receive a very good review. “Made in India, with poor surface quality.” Other firms charge more, but also produce higher quality. See http://www.dawnandevan.com/silver_core.htm for a video on this process.
There are also a number of tools that use pressure to form the core into a nice looking domed rivet. One of these is a modified thirty dollar Home Depot flaring tool sold by Art in the Round. It is practical and lower in cost. However it is not perfect.
In my use, it was performing at a 90% failure rate. 
Mostly due to operator error. The key is to place the bead firmly on the peg to assist in centering the tube. Since doing this for 3/16 inch holes the success rate went to 90%.
Also tried the tool for 1/8 and 1/4 inch mandrel holes. Not much success here. For the 1/4 inch hole the tool likes to swag one end of the flair. Perhaps again operator error plus more scrap silver to sell. This is where a dapping set may come in handy!
Overall, there does not seem to be a good way to core a bead. Some of the devices work better than others. The goal of a 100% error free tool does not seem possible. The Art in the Round tool completes the coring process much faster than using a set of dapping punches. Success at Alaska Boro for dapping is yet to be determined.
At Alaska Boro, the dapping set has arrived. Considering the number of choices on the net, this set is first class. Looked at one from Harbor Freight for 1/4 of the cost, but it had poor reviews. Made in India and of poor quality.
With free shipping for a ten pound box, Otto Frei did its homework and shipped via a large USPS flat rate box. The cost is half the Priority mail rate at $14.50 with a weight limit up to 70 pounds.
A good substitute is to use some form of stainless steel bowl. Our good neighbor knew I was looking for something that was practical and yet inexpensive. Looking at Target and Wal-Mart did not produce any desirable items.
diameter with a depth of 1-7/8 inch. Perfect for a number of projects requiring frit.
Today Alaska Boro received a very nice surprise. One of our clients provided Alaska Boro with an image of their creation using a set of our handmade in Alaska boro glass beads.