GearXS offers this Duct Tape 4-Pack in assorted colors for $7.99. Apply coupon code "H2S24" to cut the price to $6. With free shipping, that's $1.50 per roll and $6 under the lowest total price we could find for a similar 6-pack purchased elsewhere. Each roll contains 10 yards of tape with a 1.88" width.
Note that you'll receive random colors.