They do seem awfully expensive!
Coincidentally, I am in the midst of writing a piece for Sporting Gun on this very subject but you will have to stay tuned because I am not sure when it will be published.
Jon Snowdon has been using titanium sound moderators and speaks very highly of them (See Sporting Gun’s Dec 2011 issue).
But you are right, they are blooming expensive. I have not tried them myself, but I do have a titanium wrist and I shudder to think what that must have cost the NHS.
On the plus side, it doesn’t trigger the metal detector alarms at airports!
Do they work any better than other kinds? No, they don’t, because a sound moderator can only take away the boom of the burning powder; and they all do that.
None of them, no matter what the cost, can do anything about the supersonic crack of the bullet.
Which leaves us with durability.
I am sure titanium will last longer than aluminium or steel; but only if you look after it.
Neglect – in this case acids forming in the tube as it cools, and being left there after shooting – will destroy anything eventually, no matter how expensive.
So all you have to decide is whether, under your own circumstances, the lighter and probably longer-lived titanium justifies the additional cost.