As compared with most Americans, Trump’s voters are better off. The median household income of a Trump voter so far in the primaries is about $72,000, based on estimates derived from exit polls and Census Bureau data. That’s lower than the $91,000 median for Kasich voters. But it’s well above the national median household income of about $56,000. It’s also higher than the median income for Hillary Clinton and Bernie Sanders supporters, which is around $61,000 for both.Notice that the median voter for all the candidates has an income above the national norm, because of the oft-noted fact that poor Americans are much less likely to vote.
But I think it is important that despite what you have read, Trump's supporters are not people who have lost out economically. He draws support from all income groups, including the wealthiest. The core attribute of his voters is not economic pain but ethno-cultural anger.