If you get a larger drive you'll spend as much time transferring (and resizing) the image onto it, another labor to consider.

I have more often than not found that people only need to get rid of a couple GB of crud that's built up that's started giving them disk full errors, slowing swap paging to a crawl and related bad behaviors. They don't need more storage as often as they just need what they have to work the way it had been for the last 5 years.

Same amount of labor as transferring to a bigger drive, and no hardware cost. In a lot of instances cleaning up a few crumbs is all the user wants. (and needs)

This could depend a lot on the makeup of your client??le I suppose. Even before the 'recession' most of mine were telling me they had zero budgeted for any computer problems. (apparently implying "so act accordingly")