First find the length of the waist: 300 cm / 3 = <<300/3=100>>100 cm
Then find the total amount of lace she uses on the cuffs: 2 cuffs * 50 cm/cuff = <<2*50=100>>100 cm
Then find the total amount of lace she uses on the ruffles: 5 ruffles * 20 cm/ruffle = <<5*20=100>>100 cm
Then add each amount of lace she uses to find the total: 100 cm + 100 cm + 100 cm + 300 cm = <<100+100+100+300=600>>600 cm
Then convert that length to meters to by dividing by 100: 600 cm / 100 cm/m = <<600/100=6>>6 m
Finally, multiply the total meters of lace needed by the cost per meter to find the total cost: 6 m * $6/m = $<<6*6=36>>36
#### 36