Ziploc bag with a slider seal, 15c a bag https://www.amazon.com/Ziploc-Slider-Storage-Bags-Count/dp/B...
Most common trash bag, 11c a bag https://www.amazon.com/Kirkland-Signature-Drawstring-Kitchen...
And as you correctly noted, ZipLoc bags are not a staple of most households, one needs to remember to purchase them. Trash bags are in a "must have" league with toilet paper and tooth paste.