IPv6 has basically disappeared from the wireless router landscape. Try finding a current one < 100 euro. Except for some obscure releases, like the DIR-615 Wireless b/g/n Router but only the hardware revision C with firmware 3.01
Hard to find, and certainly online nearly impossible to get any assurance about the hardware revision level.
Oh wait, my good old loyal WRTG54 [V4 with plenty of RAM] to the rescue! Oh no, not now, with the current 2.6 kernel and the open source b43 broadcom chipset and it's issues. Only with kernel 2.4 and it's 'limited' IPv6 support. You can roll your own WRT54 dd-wrt, if you feel adventures but the drawback is that there is no way to use the GUI. Not a nice plan if you plan to send the devices to parts far far away from home to end users.
There is the Fritz!Box 7270 but that goes for about 200 euro. That is nearly Cisco level pricing. And only with a lab release of the firmware, that is RC in dialect in the rest of the software world. Cisco of course does support IPv6 too but using the word Cisco and a price tag of <100 is like demanding justice from a African dictator.
So is there no solution? Oddly enough, there is... and it is produced by Apple: the AirPort Extreme [ and the AirPort TimeCapsule but for a >100 price tag]. Unfortunately there are gazillion stability issues specially in combination with Apple MBP's but they do IPv6 well with a simple interface.
Not too bad! Native IPv6 ADSL for 7 euroos a month.
And Fritz!Box 7270 is indeed the only commercial IPv6 enabled home grade device available, also used by XS4ALL