This is a tricky one. Literally, Gary is right: it means that nobody anywhere is richer than you, however most people have only a limited grasp of logical reasoning and probability theory; this is why so many people buy lottery tickets. Strictly used, only Bill Gates (or whoever it is this week) could actually say this without lying, but such strictness is rare.
Most speakers would mean by this that they have a 'normal' amount of money, though I defy anybody to define that in statistical terms. 'Anybody' will probably refer to any member of a reference group of people who are socially similar to the speaker, the statement is somehow elliptical. I would use it to assert membership of a group or class that I had unjustly been excluded from on grounds of poverty; I would be claiming wealth equal to or greater than any member of that group.