As Getfurious mentioned, chains are available in different tensile stengths. Higher usually means ablility to handle more power, and also tends to have lower wear.
That being said, I have just put 37,000 kms(23,000 miles) on my Regina/JT sprocket set on my 600. Not the best chain, but for under $200 for both sprockets and chain, I'm satisfied. The factory 600 chain/sprockets only went 1/2 that before completely worn, and I might leave this set on for another 2-3000 kms. Their worn, but not toast yet, but it is starting to make some noise.
However, any chain and sprocket set had better last more than 10,000 kms (6000 miies) or I'd be complaining.