No, the amp makers are not defrauding you. You need to understand how a fuse works, to understand how to compare fuse ratings with power capabilities. A 50A fuse doesn't blow the instant it sees 50A. A fuse is designed to handle a specified amount of current beyond it's rating, for a specified amount of time. As the amount of over-current increases, the duration decreases.
Also, a peak power rating on an amplifier is a momentary rating, and nearly meaningless, but if you're going to compare fuse rating to peak power output of the amp, you need to find out what the amp's fuse is rated to handle for a time period of, say, a tenth of a second, instead of 10 or 15 seconds.
Pay mroe attention to CEA2006, or RMS power specs, and not "peak" "PMPO" nd "music power" ratings.