Janet Eastman wrote a surprisingly informative article for Los Angeles Times. You can read the article over here (Edit 2010 it used to work, but now the article is gone).
Her basic notions (for those who are busy) are:
1. 25.000 upscale log homes are built every year in U.S.
2. Nowadays log homes are convenient dwellings.
3. The average cost of log home tallies up to 120 USD per square foot but high cost areas like mountains can hoist the average up to 500 USD.
4. Typical size for a log home is 2.000 square feet.
5. Log home building technology has improved and log home quality has therefore improved.