Good bokkens are about the same length and weight of a real sword, and can be very expensive. These good ones are even crafted in the tradition of the sword system studied.
For instance this one at $85.00 from Tozando, in the style of the sword used by Yakumaru Jigen Ryu.
Ok, so $85.00 isn’t really all that expensive. Take this one for an example of an expensive bokken, also from Tozando.
It is a Deluxe Loquat Bokken, and the price is $1,045.59. Prices for bokken can fall anywhere from $10 to much, much higher as you can see.
As far as lessening injuries go, about the only thing a wooden bokken will not do is cut or slice human flesh.
Other than that, the bokken is an extremely dangerous weapon. With enough force, a bokken can still stab through soft targets, like the solar plexus, throat and eyes.
And with even less force can break and shatter bones of the fingers and hand. With a little more force these weapons can break arms, ribs and skulls.
So in a sense, yes, a person training with wooden weapons will not have to pick up their sliced off body parts off the ground, or get stitches, but a few weeks in a cast could definately be a possibility.
As could death. I can tell you, even a light and accidental hit with one of these really hurts.
Wearing armour, as samurai did on the battlefield, during training will lessen the damage taken, but in the hands of a skilled swordsman that samurai undergoing training will definately feel it when a mistake is made. Even then, the hands, fingers, and especially the thumb is a desired and usually exposed target.
These are real weapons, and the beauty is they don’t have to be used like a sword. Afterall, it is a piece of wood, and it can also be used like a short staff, but yes they hurt. Yes they can cause damage, and yes they can even cause death.