Fred Grevin, the Vice President of Records Management for the New York City Economic Development Corporation, has made a study of whether or not it's cheaper to scan documents or store them in hard copy. Fred is a principal of the Technical Committee for National Fire Protection Association (for its Standard for the Protection of Records) and he was also an instructor at Columbia University in a course on Record Management. He's something of an iconoclast against the conventional wisdom that's better in the long term to scan documents, and he has a spreadsheet to prove it.
I've posted his spreadsheet below which is now available online for the first time. You see a PDF verison of Fred's study here.
The variables on the spreadsheet are entered in the yellow cells on the worksheets named, 'Paper Storage', and 'Scanning', and formulas on other worksheets show the relative costs of each approach over a 35 year period. As you can see we can enter different costs for the price of a box; taking an inventory of a box; shipping it out and logging it; and storing it for a year. Fred gives optimistic, realistic and pessimistic cost alternatives. The scanning worksheet let's you enter different prices for doc prep; scanning per page; QCing; and indexing. With the default values entered in Fred's spreadsheet you can see that even with a fairly small number of boxes in the most optimistically cheap scanning scenario, scanning only costs less after 20 years. Fred's comments on the first worksheet acknowledge that he is not considering the advantage of being able to get scanned images on demand.
It's important to note that baked into Fred's study is the premise that each box (presumably we're considering the standard 15 x 12 x 10 banker's box) will hold 1200 pages. This may be about right if your box has several files or redwelds, but my experience indicates that a box can hold as many as 3500 - 4000 letter size pages. You may want to vary the formula in cell B11 of the paper storage field with specifies the 1200 page per box count.
Download the spreadsheet here.