Cheapest Place to Buy Baby Spinach? [VIC]

Happy to buy by the KG if needed. I want to make steamed spinach pucks for smoothies, since they're something I can freeze happy to buy in bulk.

Costco: $9.99/kg
Coles & Woolies: $25.00/kg
Rods Fruit & Veg: $1.99/100g $19.99/kg
Earthymama $29.99/1.5kg $19.99/kg

With spices I generally order off of eBay for the best quality/quantity - what's the deal with fresh vegetables? Asian grocer?