That really would make a fantastic gift for your friend, although you're right - they are rather expensive :-)
> That claim about wristwatches not being popular...
Agreed, it certainly seems obvious. I suspect at the time there may have been some advances that allowed smaller wrist watches, and that's what allowed them to take off - however that's just a guess. Women's watches at the time were quite large and elaborate, covered in jewels and such.
There's quite a good NYTimes article you might like, though it doesn't go into much detail about Santos-Dumont: http://mobile.nytimes.com/2013/10/23/fashion/wrist-watches-f...
There's also a bit more information on the Cartier Santos watch, including its modern variants, here: http://monochrome-watches.com/history-of-the-pilot-watch-par...
That claim about wristwatches not being popular among men until Santos-Dumont surprised me when I originally read it - it seems like attaching an 18th century style pocket watch to a band would've been something that became trendy earlier. Know any good articles on the topic of pre 20th century watches?