This Rubbermaid Brilliance 18 piece food storage set is $19.99 at Costco which is $10 off it's regular price of $29.99 with free shipping until Nov 22. I'm a Costco member but I'm going to guess that non-members need to pay a 5% surcharge. It's also on sale at Costco warehouse locations.
It's also available via Google Express for the same price but you pay shipping unless your order is over $35.
For comparison purposes, the 22 piece set from Bed, Bath & Beyond is $39.99 and the 20 piece set from Kohls is $44.99.