Costco’s laundry aisle is a battlefield of value. With massive bottles, bulk pods, and eco-friendly newcomers, choosing the right detergent can feel overwhelming. Here’s what’s actually worth buying. The Kirkland Signature Ultra Clean HE Liquid Detergent ($17.89 after $3.60 off, 2,041 reviews) handles 146 loads for under $18 — that’s roughly 12 cents per load. The Free & Clear version…