Rifle nades are over priced for their accuracy. I think you should lower the price because they just don't do anything. I might buy them at 60 but at 90, hell no.
Honestly? No, they should stay at this price, because you seem to forget that they can shoot just like sappers through hedges, houses and everything to kill your units on the other side. And they rock against buildings, especially if you keep them behind a building themselves, thus giving no line of fire for the enemy.
And charging them + bren, will never succeed.