Just noticed you can buy a weapon for +6. I disagree with this. +4 should be the max.
Valyrian Steel and Dawn should have a substantial advantage over any regular sword. Including upgraded ones. Its a small benefit for houses who own a special weapon.
I recommend lowering the maximum +duel sword to +4 tops. There is no way a regular bastard sword compares to a Valyrian Steel one or Dawn. Either increase the damage of VS and Dawn or lower the max sword from Bull's Wares.
There's a reason VS is a covetted sword. Its far better than iron. VS should have more than +1 or +2 over a regular iron sword. Otherwise it eliminates the purpose of such weapons. Their meant to be more sought after, not the same. Or even near the same.
Edit: From Wiki
Sum of Proposal: Decrease maximum weapon upgrade to +4. Keep maximum weapon power at 7 for VS, and 8 for Dawn. I understand the loss of power some people without VS or Dawn will feel with this, but it's for the better. Balancing measures. There is no reason an Iron bastard sword should have +6 and a Valyrian Steel sword which is lighter(faster), stronger, and sharper than it is only +1 up on it. That's absolutely silly it can even come close to comparison.:
Valyrian steel is a magical alloy invented in Valyria and used to make weapons of unparalleled quality. It is the spells and magic that make the steel special. Valyrian steel blades are lighter, stronger, and sharper than even the best castle-forged steel, and feature distinctive rippled patterns similar to Damascus steel. Most Valyrian steel blades in Westeros are treasured heirlooms of noble houses, each with its own name and storied history. It is likely that most of the Valyrian steel swords were brought to westros by the Targaryens, after the Doom of Valyria.
Regular Weapons: +4
Valyrian Steel: +7
Dawn: +8 (The Sword of the Morning is the only title that requires the wielder to be skilled in order wield it)