Which reminds me, when I worked in a tool place, diamond tipped circular saw blades were around twice the price of any other (Carbide?) and were reputed to last four times longer, diamond tipped sprocket anyone?
Such sprockets might last well but munch through chains in a matter of days or weeks!
As for sprocket wear, I had posted a photo of the sprocket on my Mercury at
http://thorncyclesforum.co.uk/index.php?topic=14576.msg109301#msg109301 . That was after 7,800 miles of which 1,600 miles was with the chain provided by Thorn and then 6,200 miles with a KMC E1 chain inside a Hebie Chainglider. I can't see much wear.