Even with the value of your house and 401k, it's still very hard to believe. I just did a quick Google search and the 90th percentile in 2001 is 1.6 million, which seems more accurate.
The top 10% includes all the people in the top .01% which skews the average higher. You might only need about 1.6 million to be in the top 10% but the average will be higher.