Exclusively for its members, Costco offers the Birkenstock Women's Arizona Birko-Flor Sandals in several colors (Black pictured) for $49.99 with free shipping. That's tied with our mention from last week and the lowest price we could find by $10, although most retailers charge $90 or more. They're available in select sizes from 37 (US 6/6.5) to 42 (US 11/11.5).