Exactly, he wins every time. The only time he hasn't won is when he can't make the game!
Last game he put $240 (12 buy-ins) into a $540 pot and still won. He's good and I don't begrudge him that but because he knows that he can buy himself back in indefinitely he plays a smart game and goes very loose hoping to catch the nuts early on to double up then bullies from the big stack position. He's a good player and I enjoy playing with him because I feel like I learn a lot and improve my game but some of the regulars are pulling out because they have never come close to the money and are not willing to risk more than a couple buy-ins.
That's kinda crazy. As good as this guy might be, and as impressive as it is to win every time he plays, it's crazy that he can contribute up or down of 40% of the prize pool with any regularity and still be profitable long-term.
Anyway, it is a real problem that you have regulars who are pulling out of the game because of this. I probably say this in every "Help! My game is losing players!" thread, but the fact that you're playing NLHE isn't doing you any favors. What John McRebuy is doing is a good example of my point: With a big enough skill gap, it's possible for a high-skill player to consistently crush a weak field.
Based on this guy's results, unless you're exaggerating or this is just from a handful of games, he's so much better than your other players that they're almost never going to beat him. It happens, but you should adjust your game to try to mitigate the damage before you find yourself at an empty table.
For one, if you make the payouts flatter, it will take away the incentive to rebuy so much because it will make it much harder or impossible to make the money back. Consider, if 1st place were ~40% of the prize pool (say, $200 or $220), he wouldn't have been able to make money on his $240 night. More importantly, it would spread the money around a little more each game, regardless of this player or the number of rebuys.
Second, I don't know what your structure is like, but faster and more gambley structures will benefit the weaker players by giving them some semblance of a chance to win by luck. With how badly this guy is wrecking everyone, you should consider changes that will cut back on the skill factor.
And of course, limiting the number of rebuys—maybe just one or two—would prevent him from using the strategy he's using. But that doesn't mean he won't keep crushing the game, of course. I don't think the rebuy structure is the main problem here, but with that said, it's not good to have a rebuy structure (or any rule) that only one player really takes advantage of, while everyone else only rebuys once or twice. Sometimes the rules have to adapt to the culture of the game.