Alright, I suppose I can see that. The main concern is that the wand of magic missiles doesn't require attunement, so a higher level character could stockpile a bunch of them and nova all the time. Though I suppose 8000 is probably enough to push the problem off until the 18-20 range.I think 8000 is still an appropriate price for the Wand of Magic Missiles. If anything, it could be lower. A Ring of the Ram (5000), used at full power, does 1.5 times the amount of damage that spending all of the charges of the wand would. It also pushes the target. Requiring an attack roll does make it less powerful, but even if we halve its damage output because it misses about half the time, it's not far behind. Being able to target multiple creatures with the missiles would be a reason to have the wand be just a bit more expensive than the ring.
Hm, I'd been thinking they couldn't overlap, but rereading it I don't think that's actually the case. I'll figure out a new price for that.Looking through the items to try to find comparable ones to the Wand of Fireballs/Lightning Bolts caused me to find the Ring of Shooting Stars at 3000. I might suggest making this more expensive, but only if the following use is viable: Using all three charges of the ring to create mini fireballs in the same area could result in damage comparable to a 6th level casting of Fireball.
I'm not sure if the mini fireballs can be stacked, but if they can, the ring should likely have a much higher price.