Beginning at the hostel, join the hostel owner on his weekly 30 minute walk to the vega. He'll take you through Barrio Bella Vista and Patronato and finally end at Santiago's famous meat and vegetable market. You'll be given a quick introduction of the market layout then set free to wander and fill your bags with fresh vegetables super cheap!!
Price examples is a kilo of mandarin oranges for US$1.50. 6 artichokes for US$3. 1 kilo of strawberries for US$2. Have a full lunch for US$4 to US$5.
Buy fish, meat or veggies for the BBQ happening at the hostel later on!