Oy, math.
This is really hard to figure out without going through all my books and since I been reading ebooks since 2008, that would take a while.
Most of my kindles (only e-readers I buy) have been paid for with shopping points or giftcards I get from doing surveys and such. Not all though, but enough that its a bit less painful. So I'd say I spend 10 times more on ebooks than I did on my e-readers? Rough guess.
I been slowing down the book buying this and last year though. Still have a pile I need to read.