>>14210830They're pretty fuckin' intense. They rival legends in Base stats.
It's important to note, though, that boosts from items do compensate and sometimes even overlap the Base Stats. Items boost more than most people think..
For example, Lucario's non-STAB (and therefore, non-Adaptability boosted) attacks actually do slightly less than normal Lucario with Life Orb. Of course, this doesn't factor in the wide array of other amazing boosts that the Mega's get, but it's important so that you realize that they're not all that broken.