The statistics I can find suggest that as a very broad population-level trend, having high income does correlate with having high net worth (though the causation could be complex). Here's some data from the federal reserve (skip to table 5 on p. 36): http://www.federalreserve.gov/pubs/feds/2009/200913/200913pa...
The relationship seems strongest at the top: the average net worth of someone with a top-1% income is 40x the U.S. mean net worth. People with 95th-99th percentile incomes are at about 7x the mean net worth; those with 90th-95th percentile incomes are at about 2x the mean net worth; those with 50th-90th percentile incomes are at 2/3rds the mean, and those in the bottom 50% of incomes, roughly 1/20th of the mean.
So the people with really high incomes (say, $300k+) seem to, as a general trend, also have substantial wealth, whether because they accumulated it, or already had it. It would be interesting to have more fine-grained data on net-worth distributions within each of those income categories.
The relationship seems strongest at the top: the average net worth of someone with a top-1% income is 40x the U.S. mean net worth. People with 95th-99th percentile incomes are at about 7x the mean net worth; those with 90th-95th percentile incomes are at about 2x the mean net worth; those with 50th-90th percentile incomes are at 2/3rds the mean, and those in the bottom 50% of incomes, roughly 1/20th of the mean.
So the people with really high incomes (say, $300k+) seem to, as a general trend, also have substantial wealth, whether because they accumulated it, or already had it. It would be interesting to have more fine-grained data on net-worth distributions within each of those income categories.