You know you're not dealing with everyday bolts when they arrive with an individual protective sleeve on each one, to protect the threads from the other titanium bolts I suppose. Since these bolts are very expensive they are used only where weight is critical, and my guess is that the dimple in the head is there to reduce the weight just a bit more by removing material that doesn't really contribute to the strength. Titanium really is very light, and you would never mistake these for common steel bolts.
The seller claims they retail for about $30 each, and I'm not going to argue with that because it makes them seem more exotic and interesting, and it makes me feel better about having paid about $3 each for a 7/16-20 stove bolt.
Analysis by x-ray fluorescence spectroscopy at the Center for Microanalysis of Materials, University of Illinois (partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439) confirms that they are high-purity titanium metal.
Source: eBay seller getnick
Contributor: Theodore Gray
Acquired: 22 February, 2003
Text Updated: 16 March, 2009