The Shanty Town was built based on Tim's instructions from earlier sessions. Though the man himself had to leave early, we were able to knock out almost an entire table's worth of buildings in one afternoon. These are ready to paint. The pink foam blocks were mostly leftover from larger projects. The cardboard came from boxes and Starbucks thermal sleeves. The wooden parts were from popsicle sticks and stirrers. Dirt cheap and effective.
We took a radically different approach for the refinery pieces. Rather than a mismatch of leftovers, we used nothing more complicated than empty (and cleaned!) soda and energy drink cans, bendy-straws, bottle caps, and wooden discs (from Michael's Crafts store) mounted on textured MDF board. Each piece had a total cost of no more than $2. I was able to build all 5 of these in one afternoon.
Though not yet finished, you can see how simple bits and pieces and a dose of creativity can produce some really nice gaming terrain that won't break your budget.