A 3DS without 3D but Circle Pad Pro-like design built into it, with a stronger battery life, and more robust graphics/features/online/eshop/ect?
Well, I wonder what the price would be. Maybe $199 or the same as when the 3DS launched. But I think it would've sold better.
With the Circle Pad built into the 3DS, it would need to have a battery half the size to make room on the right side. See 3DS taken apart video.
So the battery would be much shorter.
Plus you would also have the 2 extra buttons. So the price really would be the same. The GameBoy Advance SP still has its parallax barrier in it, even though they never used any 3D in it. So the 3D screen clearly doesn't cost much.
Plus without 3D, the pixel count would be 400 x 240. And the pixel density would be like 199 instead of over 220. And 3rd party 3DS graphics would be 400 instead of 800 native resolution graphics.
If it wasn't for 3D, the top screen would also have a resistance touch screen, and the top screen aspect ratio would be 4:3 like the bottom screen.
Without 3-D Nintendo would have settle with 2-core 268 MHz Nintendo ARM 9 CPU and a GPU max clock at 200 MHz that only does 25 million polygons. But because of 3D Nintendo uses a 2-core 1 GHz CPU and a 1 GHz GPU underclock at 400 MHz that does 120 million polygons, because the 3D effect really shows off how polygons you do & don't have. Plus the 3DS wouldn't have more then 50 shader cores (more then 360) and way more better textures & shader abilities then the Wii if the 3D effect wasn't there to show off the details of graphics soo much.
The 3DS resolution VS. PS Vita = 800 vs. 960 (thanks to 3D, otherwise 400 vs. 960)
The 3DS pixel density VS. PS Vita = between 220 & 230 for each handheld. (otherwise it would be like 199 vs. between 220 & 230, without 3-D)
What you're asking for is for Nintendo to just have native 400 graphics with half the room for the physical battery with a crappy display with with just 25 million polygons and really everyone about the graphics below the Wii, instead of the other way around. The Wii resolution is only 640 with native 640 graphics VS. the 3DS Native 800 graphics.
The 3DS only does 60 fps because that's the standard for 3D since the 1930's and it gets rid of the strobe effect. But without 3D Nintendo would have just done 30 fps, because 2D images don't need 60 fps.
The GameCube only did 60 fps because of 3D, and scared the competition to copycat with the 360 & PS3. But the 360 & PS3 can only do 24 fps and Native standard-definition graphics when they play in 3D, while the 3DS stays at 60 fps with native standard-definition graphics when they play in 3D.