It's not wrong though, the 6502 was much slower clocked that equivalent contemporaries.

However IIRC most contemporary architectures were closer to the Z80, so the 6502 was considered impressive because it was competitive despite a much lower clock rate.

1 MHz clock on the 6800 family of processors, including the 6502, is equivalent to 2 MHz clock on the Z80. The 6800 architecture used a so called two-phase clock. Each phase, positive and negative, of the clock cycle was used to do work.

I would suggest it is between 2 and 3 times, but it depends on what kind of code you are running.

A 2 MHz 6502 is approximately equivalent to a 6 MHz Z80, give or take 1 MHz depending on what you're doing.