For the sake of simplicity I am estimating the price for Sam's fabric to be
3 sm. Here is why... Skim as you wish...
Okay, so the price list has fabric prices by 50 lbs save for a few like silk and linen is somewhere on there, which yikes. Great for figuring trade goods, but scary for figuring out the price of fabric for your sewing project. I'm figuring fabric has a width of around 36" due to most pre-industrial revolution looms being less wide than what we have now - Typically at a yard or under. This means that you have to adjust yardages on all projects from our modern 45" to 60" to 36", which means you play with square yardages. I'm going to spare everyone the math I did for figuring out how many yards you'd need for making a pair of pants for a man that's 6'2" unless you want to see it.
Therefore this is my number breakdown for wool, please feel free to correct this as seen fit:
Average bolt yardage = 20 1/3 yards at 36"(12 yards at 61")
Average weight of a yard of worsted-weight wool = 10.62 lbs at 36" (18 oz/yrd at 61")
Average weight of a bolt of worsted-weight wool = 13.5 lbs
At this weight it would take 3.7 bolts to make 50 pounds. So there are 75.25 yards of fabric in 50 pounds; we'll round that down to 75 even, because your average fabric cutter will lose inches when cutting multiple pieces from the same bolt.
SO! A common fabric like wool can, as per the price list, be anywhere from 1sm to 1gm/50 pounds. That breaks down to around 27 cm to 27 sm per bolt. That breaks down to around 1.33 cm or sm a yard. We'll round up to 2.
The yardage needed for Sam's pants at a square yard (36x36) is approximately 4.5 yards. That would equal 9 copper or silver mizas per pair of pants. Since wool breeches/pants are 5 sm on the price list, it would make no sense for just the fabric to be 9sm. For pre-mades you have to factor in time, overhead, and other supplies when working out cost. Blah blah blah, I'm going with 2 sm for the yardage needed for a pair of wool pants. That would make wool around 3cm a yard.
My anal-retentiveness knows no bounds.