I doubt the used price of the 70-200 2.8 IS will go down to $1000 especially if the MKII is $2400 or so. I'd expect to stay somewhere where it is $1400 or so. The 24 1.4 mkI is still getting around $900 on ebay and that was a $1200 lens. It is the contrast of the options, $1700 or $900 for something that is still great, just not as great.