Mosfets and "power" claims

So I have put mosfet finals in two radios so far, a cobra 148 and a Cobra 29.

I see claims all over the internet of people getting 30-40watts out of them

I've only been able to get about 18watts out of either of my radios, irf530 and 13n10.

So where's everyone hiding all the magic juice! Hahaha