Naive fix for forging fine/very fine swords.
Find the value of the sword you want to make.
Find the daily salary of a smith in LTC-3.
A smith takes (cost of sword/daily salary) days to make.
Now, if you want to go variable. The weird default Margin of Success for fixed duration is 3 minutes, so assume that 100% of a day's worth of work is done on a smith/armory roll that has a mos of 3... so multiply days to make something by by 3, and that's the cumulative MoS you need to make a sword.
EG: if it takes 7 days to make a sword, that requires a cumulative mos of 21. If you have skill 15, and roll 10, for MoS 5 every day you will be finished in 5 days instead of 7.
The one piece of this formula that I am not sure about is how much should good quality materials help... I'm thinking something like you need metal in value equal to half of the finished product... but that complicates the salary calculation a little bit if we assume that salary is net, not gross.
So... coming up with some numbers, a TL 4 smith makes $900/month, and I'll say that's worth $30 a day, or $10 per MoS "Progress point."
A fine greatsword is $3,600, so, a smith needs to accumulate 360 "Progress Points" to create $3,600 worth of work.
But... they need to buy the materials for the sword and still make $900/month profit. And my ballpark "I have no idea what I'm doing" guess is that this requires $1,800 worth of quality metal.
So, $1,800 is the expense over 4 months, or $450/month.
So really they need to be making $1,350/month to cover $450/month in expenses, which really means they are doing 1.5x the work per Mos...
so the grand unified formula is:
V/(/3) = Progress Points
V is value of the item crafted ($3,600)
C is the absolute cost of the raw materials ($1,800)
S is daily salary ($30/day)
And with all the values plugged in:
3600 / [ / 3] = $3600/$15 = 240 points.