My past few averages were in the 3k range, so while I'm only half there, it is a lot of work. I attempt to limit the amount of actual PP that I'll have to do by weeding out all the bads, all the repeats that aren't as good, etc.
My typical workflow goes something like: (Note: I use LR3 for all of this, so it may vary some)
- Import all photos into LR - Create 2 collections for the imports, one is a "Temp" collection used to do the bulk of the work, the other houses all the photos. This is so I have a backup of any that I accidentally delete from the collection.
- Make a pass through the entire group (in the Temp collection) and weed out any obvious bads
- Repeat the above a couple times
- Semi-organize the photos, putting similar "themes" together. For my work, my biggest thing are the on-ride pics here, which get placed all together, organized into roughly the proper order, and shifted down to the bottom of the collection so I can find them later.
- Start going through the groups of similar items, weeding out any that fall behind the others.
- Then I start doing the actual PP work.
(I also move all HDR sets into their own collection, so they don't clutter up my actual photos...and I don't mess up and delete them when I shouldn't

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Also to note, I don't really work in an order when processing. I'll start with a clump that I want to get done, and work through those. I'll use the LR color flagging stuff to mark progress (e.g. Red = Not Touched, Yellow = PP Pass 1, Orange = PP Pass 2, Green = Ready to Go, etc). I'll also go through and give a general rating (while doing the weeding passes above) which lets me focus on a general area to process through.
For the past 2 trips, I started with ~3.5k photos and ended up only having to actually process ~1000 and only have to do real work on about 500-600. (Some of them I'll pop some color balance, light cropping, etc, but won't really pay much attention, these are essentially the "Decent Family-Style Vacation Pics" rather than the ones I really want to share)