Deep Impact increases damage by +1 and multiples the cost of a weapon by 5. Blunt reduces damage by a whole die step and divides the cost of the weapon by 5. That doesn’t seem enough – given a die step equates to more than a reduction of damage by 1. On that basis, I would suggest that Blunt divide cost by 10, not 5.
As an example, a Training Baton – a wooden sword-shaped sparring ‘blade’ used by many establishments to provide basic guidance in handling of weaponry to children – is a Blunt Improvised Weapon, which inflicts 1D2 damage (flip a coin or roll a 1D6, 1-3: 1, 4-6: 2) and costs 2 Ortegs (base: 20 Ortegs / 10).