I think the two best selling points that Thesis has is the amount of information out there on it as it's one of the top selling themes and the hooks. You can do some amazing things with Hooks and there is plenty of forums/blog posts on how to use them.
Also, it has a bunch of SEO built in that is in the all in one SEO pack, so you don't need it. And one less plugin means faster load speed, which Thesis seems to be one of the faster loading themes if you don't junk it up with a bunch of nonsense. Speed = cash.