Yes but I am not in an accounting class. A consumer loses
$$$$ as a result of depreciation not percentages on a piece of paper. Your math is 100% correct, but what does your wallet lose? Could you have sold a GTX580 for $350 when HD7970 just launched? Yup. What about HD6990 for $600 when 7970 just launched? Unlikely. When the 7970 launched, used 6990s were going for $450-500. A car depreciates much worse than a videocard in monetary terms. That's key right there. Which videocard loses the least amount of $ "renting it"? Sure in % terms a car holds its value better over 5 years (let's say 40-50% of its retail value), or that 6990 holds its value better using your math, but in the end all that matters is actually how much $ you end up losing, not %s. If you bought a $10 million house and lost 10% of its value, that's a terrible investment. If you bought a $500 videocard and lost 50% of it's value, it's manageable
Using monetary context (which is the only thing that matters when you are spending it), not accounting definition of depreciation, a 6990 and a car are much worse depreciating assets than the 580 was, since you'd lose more $ owning either of those. What I am saying is the 6990 loses a lot more value (i.e., money), and it's super hard to time the resale of the 6990 against say 2x 6950s when 7970 launched. Using the same logic, relative to what happened in the past, a gamer is likely to lose more $ buying a GTX690 I bet than 2x 680s or 7970 Ghz Edition x 2 vs. a 7990. I've been reselling cards for a long time now and I've come to this conclusion based on my market. I am sticking to what I know in my market. Other people should stick to what they know. If they can flip a 690/7990 without losing a lot of value compared to 680x2 / 7970 GE x 2, then that's what they should be doing. I know I'll be able to resell 2 7970s for more than a 7990, so I won't touch the 7990.
If based on your experience, there is no large loss of buying a dual-GPU single card, then that's great
In my market, there is a huge penalty for buying dual-GPU cards. In UK for example, some people say that dual-GPU single cards hold value better than 2x single-GPUs. So it depends on the market I suppose.
Plus, I don't use EBay at all because of fees. I get way better resale value on Craigslist and Kijiji. It's in-comparatively easier to sell a single-GPU card due to the size of the target market. I can go out right now and sell a 680, easily, but it'll be a while before I can readily unload a 690 at a good price in person. This is because the market for people who want a single-GPU used card is
huge, compared to the 10-15 people in all of Toronto who'll want a Devil13 card 12 months from now and probably 3-4 people who'll want it in 2 years from now. I followed prices of 4850X2, 4870X2, PowerColor 6870X2, GTX295, no one wanted those cards after a new generation. Now 6990 is only going for $350, but I doubt that person will even get that, which is more than a $500 loss of $$$, not %s. Used 6950s go for $180-200, which means $170-175 real resale. That means the 6990 was a terrible option vs. HD6950 Unlocked which only cost $565 and resold for $350.
I think the take-away here: People should stick to their personal experience. If in their market, they can sell a dual-GPU card without a significant monetary less against 2 single cards, then this doesn't present an issue.
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More pictures and info on the 7990 Devil 13 card. Looks like it'll be a power hungry beast.
http://videocardz.com/34576/powercolor-announces-radeon-hd-7990-devil13-6gb