The context that may be needed is if you used something like Amazon Glacier or a tape drive as the final resting place for old images. Keeping data on spinning disk has a cost. If there are 3rd party costs, those will need to be accounted for.
Plus, I would want to temper the context of what was originally delivered & what was stored. If you previously delivered jpeg's & have those files stored somewhere, it's pretty easy/cheap. If you don't have those jpeg's now, and would have to do extensive exports of PSD's or raw files, then it would be more involved & the price should reflect that.
If you're exporting fresh jpeg's, it's worth looking over them & making sure the colors are accurate.