I'd kinda like to see whats out there before naming a price. I don't think I've seen another overcapped bokuto. I'm sure they exist, just haven't seen one. Its much easier to loot one with 20 splinter and lower d or lighting than it would be to loot one overcapped on splinter with or without useful secondary mods. The rarity should make it worth more. I also suspect most players would prefer 20 splinter and 50 lower d or hit spell to one with just 25 splinter even if they'd really love another 1/20 chance at a proc. This should depress value. Thinking this through I guess I'd ballpark it at around the same value as a 20 splinter 50 harm bokuto.
I'm open to offers. I'll watch this thread and if no one responds with anything else then I'll send you a price via PM.