wait, you think 5Ds are holding their value? They were originally MORE than the 5Dii is now ($3000, or was it even more than that?) and are now selling for around ~$1500? That's a pretty big hit IMHO.
If you don't want to get "burned", don't buy new/early and sell late. The key is timing your purchase so you don't pay full MSRP (rebates, used, sales, whatever) and then sell it BEFORE the new model comes out. This way you buy in below the original sticker and sell before the price DIVES....
also, the 1Diii is a bad example because of the AF issue.
but, for example, my last 2 bodies? My 1Dii I owned for 18 months and sold for $400 less than I bought it. I bought it on the rebate and sold before the 1Diii came out. My 5D was picked up "slightly used" and sold for $400 less than I bought it for, also 18 months later. Now I sold it BEFORE everyone else dumped their 5Ds for the new version, and I also picked up my 5Dii for 3% off, tax free and no shipping (I'm an affiliate, I used my own links
). I was thinking I'd keep the 5D as my body a lot longer (it wasn't a needed upgrade) but the bells and whistles of the 5Dii caught my attention, as did flipping my 5D for my <$500 loss number.
And one last point. Regardless of how much you "lost" on a body, calculate how much each shot cost. If you're <$.25 per shot, you've saved a ton of money over shooting film. So don't look at is as a loss on the body, but a savings per frame. Electronics depreciate, so you just have to time things right. It's funny, but I'm thinking about getting another 1Dii again. I sold my last one for $2800 and could now get another for less than half that (and possibly even a 1Dii'N'). So, to me, it's about timing.
But I do expect to keep my 5Dii for a LONG time (basically, the mark III probably won't tempt me, a 1Div could if it's a merge of the 2 lines).