Personally, I don't even think there is a contest here. The 2000 should stay. The 3000 is a nice machine, but, it was always the orphan with very little hardware support. On the other hand, everything worth while ever made, was made for the 2000.
Not sure about other models, but, my 030/25 3000 was a dog compared to an GVP 030/25 A2000 that I currently use. Also, the onboard SCSI isn't really that great either. All of this taken into consideration, plus the pain of zip rams and lack of real estate inside the case, and the A3000 is a nice looking machine, with not much going for it.
I will admit, the 15 pin VGA out is nice, but, with the availability of scan doublers from places like AmigaKit which fully support the A2000, that's really not a selling point.
The good news is, you are correct that you can fetch a kingly sum for the 3000 because for some reason people slobber over these machines and are willing to pay big bucks for them.
If it were a 3000T, that would be different.
I also should mention that I am an A2000 nut, and have owned many of them over the years. So, I am a bit biased. ;-)