Foam boards, which form the basis of the model, have been a staple of many of my recent projects. They're light-weight, strong, smooth, and easier to work with than cardboard, though not as cheap. But they can be cheap; they recently started showing up at Dollar Tree (for $1, as compared to $3 at craft stores). Wal-Mart was great for glue, tape, and spray paint. Lowe's was good for PVC pieces. Other parts were found at craft stores or online. A rough budget estimate on the materials of the statue:
Plaster Strips - $60
Foam Boards - $42
PVC Pipe - $20
Spray Paint - $15
Hot Glue Sticks, Mod Podge, Wooden Dowels, Water Noodles - $28
A grand total of about $165. All things considered, pretty modest for something of this scale. I'd first found plaster strips at craft stores, but when I started needing them in large amounts, I turned to Amazon.com, which had the best deal on a bulk package of plaster strips.