The real problem is that these cards came out at different times and have a different target in the market. Add to that the fact that both nVidia and ATI want to promote that "newer is faster" and you've got a mess.
chronologically this is what happened on the ATI side:
Product: Target Market Segment
Manufacturing and Marketing Issues
8500: Extreme High-End
Expensive to produce, but it doesn't matter since it commands premium price
8500LE: mid-range
8500s that can't quite clock up to full 8500 standards are redged as LE's and sold cheaper (still expensive to produce)
9000/ 9000 Pro: Low-end / lowish mid-range
8500 series is discontinued. The part is cheaper and easier, to manufacture but the performance is slower than the 8500's. This card is supposed to replace the 7500 in the low-end segment in the (9X00 time-frame, since it is based on the 8500's core it naturally gets compared to the 8500/8500LE. Unforseen: demand for the 8500 remains strong while the demand for the 9000/9000 Pro isn't so hot.
9700/9700Pro: Extreme high-end
Flagship product, killer performance but killer manufacturing price too. Functional 9700 cores that can't quite clock up to Pro clockspeeds are sold as plain 9700s to OEMs much in the same way the 8500/8500LE system worked.
9500/9500Pro: mid-range/ highish mid-range
After the 9700 Pro is released, there is a void in ATI's mid-range market segment. The solution, take failed 9700 Pros cut the defective pipelines and memory bandwidth and place them in that segment. However, these cores are still expensive to produce and make precious little profit in the market segment they are placed.
9100: Lowish mid-end
A reaction to the 8500's continued success, ATI rereleases it with a new number for marketing purposes and to reflect that the performance is higher than the 9000's performance. This revival is short lived and is basically just there to get rid of remaining 8500s.
9800Pro: Extreme high-end
Tweaked 9700 Pro: ATI has gotten better at producing 9700s so they can release a higher clocked version. Cores that can't quite make it to 9800 speeds are likely being used to produce 9700/9700Pros now.
9600: Mid-range
13µ component meant to replace the 9500/9500 Pro. Much cheaper to manufacture for ATI, though it is slower than the 9500 Po a stock speeds. Mainly makes the mid-range profitable again for ATI, who are discontinuing the 9500/9500 Pro, since they are so expensive to manufacture.
9200/9200Pro: Low end
9000 Pro with AGP8X added. The 9200 Pro is also clocked up a bit. Still defeated by the 8500/9100, but these products should no longer be on the market so that shouldn't make a difference to the unaware.
And there you have it, a quick recap of why and how ATI ended up with a messed up numbering scheme. Take one part marketing, and one part manufacturing optimization, add a dash of nVidia competition. Stir until you have a modeling scheme that makes no sense and VOILA the Radeon numbering scheme.
I'm sure someone could do the same for nVidia if they wanted to.
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