It's simply a matter of ROI, and even though miners have scooped up hardware left and right, it's only been specific hardware lines with specific features (the desirable ones you mention), and at the same time we're not willing to pay too much for them.
Their bread and butter is still the considerably larger gaming community who were happy, even eager to pay $350 for a 5850 when they were new, and the even larger 'low-end' market picking up GPUs that we wouldn't consider worth the shipping fee.
The simple fact is it's not currently worth it to develop a line of cards tailored to bitcoin mining. Not to mention that revenue stream could dry up in an instant if bitcoin happened to fail hard.
Why the OEMs aren't scrambling to reduce the prices on otherwise slow moving 69XX series cards, or pumping the market with tried-and-true 58XX series cards, I don't understand. They've already machined their tools to build them, gone through a few iterations to get things just right, and are likely high into profit on these cards.
Produce a lot more of them and they'll still sell faster than they can get to the shelves, and they don't even have to reduce their pricing model. While I don't expect to see mining-specific cards, this is a no-brainer.
Then again, seeing Newegg selling $100 5830s, when they've been disappearing in minutes for $30 more, feels a little like market saturation testing by the OEM. Perhaps Sapphire will heed my advice.