RealityRush :
Uhhhh, I'm pretty sure that ATI/nVidia have deals with their chip manufacturers that they get a discount based on the percentage of faulty chips and the yields, etc. So the 5850/5830/470 chips do NOT cost the same as a 5870 or 480. Correct me if I'm wrong TGGA.
Deals are pretty hard to know and change alot with production variables even cost per wafer are tightly guarded early in the process. They likely get some discount with the early debacle in 2009 and early 2010, but usually you don't get a discount for poor yields due to design so much as due to process. Yields have improved on the 40nm process overall so likely the option for discounting is no longer offered.
Here's the thing, you guys are both kinda wrong and kinda right.
First the chips cost what the chips cost, you pay for the wafer, not the final chip, so if you get a discount due to poor yields then you get $1,000 off the cost of the wafer, not $20 for an HD5830 and $10 back for and HD5850. So technically the 5830 costs the same as the 5870 at the die level. Although remember before they added the 5830 SKU the value of the chips that could only make that level of usefulness were unused and essentially garbage, so the HD5830 chips are essentially gravy left over from cooking the prize Goose (5870/5890) and Chicken (5850) which are the ones that are built in to production so you could consider the cost of production for the 5830 dies as 0, or else you cost average them with the other two (thre if the HD5970 is a speed binned 5870) chips. Alot of that depends on how 'built-in' the HD5830 was/is to production plans.
Poducts like the HD5830 and likely GTX460 are only added if there is a high enough defect rate that you can create a production SKU from the garbage bin that is worth putting onto a card and marketing. Any profit you can get from them means you reduce the overall cost of production which helps all products and could turn a money losing design into a break-even or profitable design, or speed up the ROI on R&D and give you the accounting option to move on if you want to (although that's more a justification than a plan often, since you want to wring out as much money as you can, but also always be pushing forward). But remember that's ATi's side of the equation, they just sell the dies and then bang it's gone to the AIB for the next step, so it may be considered as a 0 cost product, but it ends at ATi.
Now it's time for the AIB who definitely doesn't buy the HD5830 chips for $0 so then you get into the marketing and deals for those, is the pricing 150/100/50 ? and does AMD require you buy a certain number of each before being offered the HD5830 chip, or even the other way around if the pricing is higher where they require you to buy X number of the 'garbage' in order to get the golden goose, etc (this is supposedly the case with Fermi where AIBs are forced to still buy G200/G92 chips in order to get any allotment of Fermi chips).
The other thing about this is the cost of producing the boards, the HD5830 board doesn't cost as much as the HD5870 board let alone 5970 board, so for the AIB it's a combination of the two and that influences their costs/pricing depending on the cost of making the additional boards and such, but usually the low end card (GPU+board) costs significantly less than the high end cards to make.
Hope that helps explain it.