Using Amazon for this, it is hard to know the actual cost for Levi's fabric, fair to say it'll be lower, but we'll work with what we got.

You can buy a 5 Yard Bolt - 60" denim for $32,95. I'm gonna convert here because I'm raised metric and will get it wrong if not. 5 Yards is 4,572 m and 60" is about 1,524 m so the surface area of a sheet is about 6,967 m2.

Eyeing a pair of my own jeans I'd say the actual pocket is about 8,500 cm by 6,000 cm in or 51,00 cm2. Per bolt we'll get 1 363 coin pockets for our 501s, and one pocket would then cost $0,02419.

501s on Amazon costs between $26,63 - $69,50, median being 48,07. Link

If we go by this site Levi's total revenue for 2016 was $4 494 000 000, if we turn that into number of 501s sold that makes about 93,48 million pairs of jeans.

At $0,02419 saved per pair of jeans sold it would seem that Levi's would save around $2 261 000 dollars on their pocket saving venture.

This would amount to 68 620 bolts of jeans fabric and weigh about 277 tonnes or 610 700 lbs. A semi can haul a maximum of 80 000 pounds and it would therefore take 8 trucks to haul the fabric to the factory. Using this site the cost of hauling would come down to $32,42 per US ton shipped or $9 903 for the whole load. I'd say this cost is negligible on a whole.

Edit: shitty formatting ^{^}