Another major difference is the price point. IIRC SEv1 cost over $1000/mo for a community to organize a Q&A site, which not many could afford, let alone had the community to need that many questions and answers. So SEv1 cost too much for you to not use it.
Where as if this is priced in the $10-99/mo range, you wouldn’t need a very active community to get $50/mo worth of usage out of it. After all, what is $50 - Taco Bell and a movie. With that low of an entry cost, way more communities will be able to be hosted, and since they wont need many resources, they can be hosted shared, costing way less than an install of SEv1.