The average pts per food sack is about 2.2

50 Exquisite Silk = 50 * 20 = 1000pts

1000/2.2 = ~450 food sacks

450 * 10 = 4500 coupons

Cost for 50 Exquisite Silk (Without Daily Free) = 4000 to 5000 Coupons (Give or take 500 depending on luck)

Cost for 50 Exquisite Silk (With Daily Free) = 3750 to 4650 Coupons (Give or take 450 depending on luck)

25 Exquisite Silk = 25 * 20 = 500pts

500/2,2 = ~225 food sacks

225 * 10 = 2250 Coupons

Cost for 25 Exquisite Silk (Without Daily Free) = 2000 to 2500 Coupons (Give or take 250 depending on luck)

Cost for 25 Exquisite Silk (With Daily Free) = 1700 to 2100 Coupons (Give or take 200 depending on luck)