The 670 is the fourth-ish most powerful video card out there. That's not mid-range. It's the bottom of the high range. (Or you think the 680 is high range when the 670 isn't, in which case you're going to get laughed at.)
Yes, there are very expensive graphics cards... but they're either workstation cards or dual-gpu cards. If you buy two 670s, you have the performance of a 690. But that doesn't mean that the 690 is the only high end card, it means the 690 is a niche card.
We fully understand you perspective - as a seller looking to maximise profit but! our/tom's side of the fence is a little different.....the vast majority may have some difficulty - you might want to taper the 'seller perspective' in favour of the majority of forum members.
That's another niche, if possible of course it's better to sell the highest card or dual gpu.
But for the consumer who buys the card individually and it's well informed, he knows it's a high-end card, and that for gaming the 670 gtx is on the level with the 680 gtx, which is the top card single gpu.
In terms of performance, excluding costs of the cards, or marketing, as high-end card it has about the same fps as a 680 gtx or 7970, and there are versions who are better than the stock 680 gtx.
High-end purely in terms of performance.
690 gtx or 7990 is another story, then again i can bet that any guy who buys a 670 gtx has a motherboard with SLI, which by adding a second one tops the 690 gtx.
You forgot the top of the range 7990 ( I run one) and the 690...
No I didn't.
gtx670 is slower than 2 other single-GPU cards on the market: hd7970 and gtx680.
7990 and 690 are cards for people who either like to waste money, don't know what they're doing, or somehow have a high-end rig with only one PCI-x16 slot. If they didn't have a huge premium I could see using one of the dual-GPU cards as part of a tri-GPU setup, but they're more expensive than equivalent two single card setups, so both models are basically worthless to anyone who knows what they're doing.
If you're building for clients I can see why you'd use them in builds, but they're not for regular, knowledgeable consumers.