For everyone else who wants true-silvered weapon, here's your answer.
-Mithril (True Silver)-
-Add the costs of Mithral and Silver.
[500 gp/pound + (20gp - Light Weapon) or (90gp - 1-handed) or (180gp - 2-handed)]
-Don't use the -1 damage Silver Disadvantage.
-Don't use the 1/2 weight Mithral Advantage.
-Allow it to bypass Silver DR.
Now it really is "true-silver". Note that the rules specifically ban this combo in the silver entry "...it doesn't work on rare metals such as adamantine, cold iron, and mithral.", so this is clearly a house rule. There are still reasons to get silver weapons (cheaper) and mithral weapons (1/2 weight). The hardness/hp is a mix of hardness from mithral and silver. I used the common values for weights to derive prices for weapons:
Ammunition 5/1lb
Light Weapon 2.5 lb
One-handed Weapon 5 lb
Two-handed Weapon 10 lb
Hm. Turns out a Mithril Greataxe costs more than an Adamantine, Cold Iron, or Silver Greataxe. Since Adamantine is the best (as it gives a nice "ignore hardness <20") and costs 3,000 gp for any weapon, I based the price off of Cold Iron (in that for any weapon it costs about 2,000 gp) with reductions in price for weapons with less mithril. So the price per pound ends up being about 200 gp/1 lb before adding in masterwork costs. The cost for light weapons and ammunition are roughly 20 times as expensive as regular silver (so 1 mithril arrow is as expensive as 20 silver arrows) while one-handed and two-handed weapons are only about 10 times as expensive. For masterwork I just added 10 to ammunition (for a nice round 50), the full 300 to light weapons, and 250 to one and two-handed weapons.
Everything ends up being quite a bit cheaper than mithral, but it doesn't give the main benefit of mithral (the lightness) and, imo, the designers of 3.5 decided not to mess with mithral weapons at all (rather than design a stronger silver, which wouldve been cool).
For everyone else who wants true-silvered weapon, here's your answer:
Mithril: Mithril is an alloy of silver and mithral, but stronger than either. When worked like steel it becomes a powerful material which bypasses the damage reduction of creatures with DR X/Silver, such as lycanthropes. Only weapons normally made of metal can be fashioned from mithril. Mithril is sometimes called "true-silver" among dwarves and elves, and orcs tend to fear it.
Weapons fashioned from mithril are always masterwork items as well; the masterwork cost is included in the prices given below.
Mithril has 30 hit points per inch of thickness and hardness 18.
Type of Mithril Item/Item Cost Modifier
Ammunition/+50 gp
Light Weapons/+800 gp
One-Handed Weapons/+1,250 gp
Two-Handed Weapons/+2,250 gp
Technik