Can't speak to how this approach would 'cost compare,' however, I have dealt to my satisfaction with both your stated matters (fenders, et.al., + empty fuel containers) by simply giving my entire rig (bike, panniers, & then some) to REI at one location and had them pack/ship from one REI location to another REI location close to my tour start point. I have taken this approach at least 3 times and will continue to do so IF, of course, REI locations are in proximity to my tour start and stop sites. I saved more time on 1 or 2 of those occasions by paying REI to reassemble/test out my bicycle, as well. Coming home I always had the option of having them pack/ship straight to my house.
Last time I tried that they said the policy had changed.
That was in 2012 at the Denver store.
Have you shipped that way since then? *
Wow. Your update is important. Thx. * Nope .... my last was just before 2012. At that time I did one of the Atlanta REIs to Spokane REI.