The problem with your analysis is the person who bought the mac really did pay $1200
BS. I have never paid retail for a mac. Looking in the archives just like you did, 2010 postings, what's this- 13" macbook pro new for $1049, another posting for $999.
I've sold my macbooks every 2-3 years since 2005 and have always gotten around 70% back (though I do take ridiculous care them, even keep the original wrapping inside the box).
I see thinkpad threads in 2010 for the 410 going for 700-800 at best and some in the 500-600 range so with your scenario, PC still comes out ahead...
Cheapest I saw for a T410 new (not refurb or end of 2010- making it a year old model ) was $650
So, Macbook bought $1050, sold in 3 years for 700, cost $350. Thinkpad, bought for $650, sold for $300. Cost $350. Seems even to me. And that's with a highly regarded thinkpad, try selling an Asus or Toshiba for 50%.
Which brings me to my final note.
Macbooks are just easier to resell too, simply cause there's less of them, both in quantity and models- Apple might have 4 different 13" in a year. PC maker, 12+, and that's just one manufacturer. There are sooo many pc laptops it makes reselling one a bear.