Timeline?
250,000 pages is going to take an eternity with just one unit. You may be best off calling up your office supply places and asking if you can rent equipment for the project.
If you can, I'd test something like this. Machines like that scan a lot of documents a lot quicker than a flatbed scanner. I'm not sure how they'd deal with labels and such without an example (pictures) of the kinds of things that would need to go through it.