As just one example, this spec of a JBL 15 G2 says:
300 watts low-frequency and 100 watts high-frequency (bi-amplified) - actual power delivered to the drivers.
and also says:
110 - 230 VAC, 50 - 60 Hz., 175 watts
I can only imagine that these ratings are being measured differently. But I can't figure how.
(just to make sure it wasn't simply a typo, I found another example : 500W RMS speaker power, 130W power supply)