Like young Markus Johnson said, his power is maximum.
Okay, but seriously, I'd say his power is equivalent to a fully developed Super Saiya-Jin, he was merely born with the ability to turn Super Saiya-Jin. In movie 8, the characters (aside from Brolli himself) are considered new Super Saiya-Jin (they've all been Super Saiya-Jin far less than a year, for example), while Brolli himself has been a Super Saiya-Jin all his life.
A basic Super Saiya-Jin's power is damaged easily, and his energy drains quickly. A Super Saiya-Jin takes time to develop their abilities, and learn how to properly hone their power in this state. Yet, in Brolli's second appearance: Super Soldiers never Sleep, he kicks the crap out of Goten and Trunks (basic Super Saiya-Jin), but when he goes up against Gohan it's a much more even match.
This could be attributed to the fact that Gohan became a Super Saiya-Jin several years prior, and his Super Saiya-Jin power is fully developed just like Brolli.
So, I am going to have to disagree with the ever climbing theory, because after all, this is more something to attribute to True Buu (aka 'Kid Buu'), who actually did have his power ever climbing once he was no longer tainted by Kai?shin goodness.
Born with 10,000 power? I'd agree with that. But Brolli was far worse than a planet destroyer -- Brolli destroyed the South Galaxy.