North American lumber prices have crashed in a short time span, taking only eight weeks to tumble 70 per cent from record highs as the party ends for forestry companies.  The price sawmills charged wholesalers – known as the cash price – was US$485 for 1,000 board feet this week for two-by-fours made from Western spruce, pine and fir (SPF), compared with US$1,630 in mid-May, according to Random Lengths, an Oregon-based company that monitors wood markets.  “The deep slide from record-shattering levels extended to an eighth week ...