Andrew Gelman claims on his blog:
Upper-income people still don't realize they're upper-income
If people are directly asked whether they consider themselves to be upper income, do they underrate their relative wealth?
The blog makes that claim that upper income people don't think they are upper income because of discrepancies in the answers to two questions, asked of "upper income people". Specifically, "Is the amount of tax you pay too high, too low, or about right?" (to which most answered "too high") and "Do upper income people pay more or less than their fair share of tax?" (to which they mostly answered "less"). But there's a disconnect between the two questions. It's perfectly possible to believe that taxes are generally too high (including taxes on themselves, as upper-income people), but that upper-income people (including themselves) pay less than their fair share.
"Upper-income" is not a well-defined term, so if people don't consider themselves "upper-income" that's their opinion, and doesn't reflect a "lack of understanding" at all.
Looking for evidence to actually answer the question, I found this. It shows that people massively underestimate the fraction of wealth owned by the top few wealthy percent. In that sense people maybe overestimate how far up the income ladder (technically wealth ladder) they are.