Hi Turnoi,
As one of those 'low profile' teachers at EF (I have a degree in Linguistics and am working on my masters degree in Applied Linguistics and TEFL, aside from my CELTA qualification and previous experience) I would value a better indication of what you mean by a 'bad business model'. I'm not suggesting that everything is perfect in EF Shenyang, but what I'm looking for in a school is:

A dedication to professionalism and a high standard of teaching.
Support for teachers, including good quality resources, a training structure and a positive environment where teachers help each other.
A good relationship with the leadership (new ideas from teachers taken on board, a flexible schedule, a fair workload, mutual respect etc.) .
A reasonable salary that is paid on time.
Opportunities for development, a bonus for good work and rewards for staying on in the school.
A flexible schedule (again) with no office hours: important as I also study and work as a translator in my free time.
The ability to plan my own lessons and structure a course around a coursebook - there are some schools where teachers basically do what the Chinese staff want them to do, or are given a lesson plan to teach. It's important for me to gain actual teaching experience which I can use later.

There are a number of other things that I value (such as having help setting yourself up in a new city and for someone who will fix any accommodation problems in good time) but as you can see, the salary in itself is just one of a number of priorities for me. I'm quite aware that there are schools that pay more (and I'm sure a good number of them would fulfill my criteria too), but I'm really not looking to get the highest salary possible in my work. If you want that, you really are in the wrong job anyway, as we're talking about a difference of a couple of thousand per month when you can easily earn four times a teacher's salary in other jobs as a foreigner. As other people have mentioned, EF seems to be doing fine despite any great failings in its business model - the salary may not be that high but there are many other reasons keeping people there.