Get up to 15% off Las Vegas vacation packages, then take an extra $50 off when you use the code LUCKY50 during booking at Southwest Vacations. The offer requires a minimum stay of three nights. We found one three-night package at the Cosmopolitan, including round-trip flights from Chicago for two people, for $1,207. It drops to $1,157 with the code (about $579 per person). Book by 4/3. Travel by 9/29. Taxes and exclusions may apply.