It's like keeping jugs of water in the refrigerator: the system works by cooling the air, which falls out when you open the door. The space taken up by the water means there's less air to fall out.
In any case, your analysis of square footage is clever, I hadn't thought to consider that cost.
If the square footage would otherwise be empty my whole point falls apart.
Actually, more mass (book mass, or any other kind) does make HVAC cheaper: http://static.monolithic.com/pres/rvalue
The California Handbook for Solar Energy is the only government publication we have been able to find which takes into account the thermal mass of the concrete when measuring heat loss. Simply stated, the concrete acts as a heat sink which slows the passage of heat back and forth through the wall or roof assembly.
This shouldn't be over looked. My wife and I have moved twice and both times we had to cull our "library" in an attempt to save space and weight.
Figuring an average moving cost of 60 cents per pound and 1 pound per book, moving costs for books can add up very quickly. And forget about it if your moving across an ocean. With e-books this cost is negligible.
I guess you could replace the clutter with something else (another comfy chair?) but I'd rather have the books.
Also, lots of useless clutter isn't usually very good for your sanity.. :)
Also I don't think the medians you cite are anywhere close to correct. Maybe they're correct as medians only within the US? I remind you that the US is less than 5% of the population.
Otherwise your figures look good to me.
Maybe the right answer here is to pay attention to your current region. I'm paying about US$350 per month (before taxes) for 60m², about 600ft². For me 40 books per square foot means each book costs about ⅝¢ per month to store. I think that's about US$0.68.
2.50 / 30 years = about 8.33 cents per year in 'storage rent'.
Seems pretty cheap to me, when you compare relative costs of storage.
Of course, I'm typing this with some sarcasm, because the whole metric is bad. Your analysis assumes that: A - somehow you have unlimited items to store in all the empty places in your house, B - ignores the absolute cost of having empty space (you've already spent on the house, but if you leave that space empty, you have opportunity cost becuase you COULD be storing books), and C - ignores any utilitarian value you get from having the books around. :)
Here's a hint: C is most important. And it references back to the point the article is trying to make.
It is clever though, so I'll give you that.
I'm a reasonably well compensated developer in the Boston area and it still seems high.
I'm in the exurbs of Boston, and 200K as median just feels bubbly.
I just measured some books I had and 10 books per foot by 4 shelves high yields a minimum cost of $2.50 per book to store. This does not factor in moving costs of the lifetime of the book nor energy costs to heat/cool the books.
It is surprisingly expensive to keep 'stuff'.