Sorry to inform you I don't believe there is any such thing as
cheap lumber anymore. Unless you come across a lucky find.
This is what I've suggested in the past. Try to locate fellow WWers in your area. Collectively purchase a large load. Typically 3K bdft will bring down the price considerably and you'll normaly be able to mix species at the discounted\contractors price from a real lumber yard, not a home center.
In order for the separator to work correctly, you need to set up a "cyclonic" action inside the can. This means the intake is near the outer edge of the can and a fitting directs the air flow around...