I'm a firm believer that the 24-105 is valued at $600, since that's the typical price premium on kits that include it. You should be able to get them new-in-box for $599 from many folks who bought the kit and want to unload their lens unused. I'd suspect Canon's fee for clean/check/simple repair to be around $225 (we paid $216 for a simple repair on our 16-35/2.8II about three years ago). I'd keep all of that in mind as you make your choices.