In Germany, the tty bolts are common... not cheap, but common. They put a lot of stock in the technology.
In situations, they are the ONLY bolt. Head bolts, for example (sorry, but even ARP bit the bullet and makes TTY's for certain diesels).
That being said, there is a limit to the insanity. Once bitten by the TTY bug, the Germans seem to have gone over the top.
For example, I have recently finished the preliminary engineering for reusable bolts in the PD cylinder head. $100 just to look at the camshaft for TTY's is absurd.
Part of the reason is what happens to aluminum threads when using a harder bolt. If a 12.9 bolt is used in place of a 8.8, the 'stretch' is diminished greatly. The torque becomes the critical measure. Where thermal expansion comes into play, the torque becomes even more critical.
The proper torque is a problem due to frictional forces, which can be as much as 60% of the total torque. The TTY bolts overcome the problem of variance in the frictional force when the bolt 'gives' at the proper clamping force.
I ran into an interesting site that helps with much of the issue:
http://www.boltscience.com
It's a primer on bolt technology and application. Although it doesn't get into all the angles of the TTY's, the big issue is in commercial application, rather than having a very finicky and exacting method of installation, you can 'hammer it home' , within limits, and it works great every single time.
But given the aftermarket and especially a few arguably 'damned expensive bolts', I found the proper torque, eliminated the frictional barrier and have a very good solution for the PD cylinder heads with relatively cheap and reusable bolts and a very accurate torque and the use of moly grease.
Btw: another thread mentions "Do you use Anti-seize on lug bolts?" The answer is NO! DO NOT USE IT! That bolt is particularly high frictional load. If you eliminate the friction, you have to reduce the torque a great deal.. at least 30%. Given the importance of the fastener, I wouldn't mess with it. Over-torquing is as bad or worse than under-torquing. In the end a snapped bolt is as bad as one that comes loose.