Disclaimer: I have an MBA from a top canadian school (that does OK on global rankings) from a decade or so ago.
The true value of an MBA is the doors that it opens up from to the connections you make in the program. The actual learning if you compare a top 10 ranked global school and a top 100 school won't be the that different and definitely won't reflect the potential cost difference between some programs. However, in a top 10 program you will be learning with other high performing successful people who have also met the high criteria to get into the program. You will have access to the alumni network of that school. You will also have access to corporate recruiting programs that the school has established with desirable employers.
Id add that an MBA today isn't what an MBA used to be. An MBA used to be close to a guarantee to give you a boost to your career. Today they're really a dime a dozen so unless your coming from a top school, you really need other strengths to help you get where you want to go. I am involved in hiring in my role and its surprising the number of people I see that have an MBA of some sort on their resume but are in very junior roles.
I am not familiar with the No Pay MBA. However, I am familiar with edX courses.
https://www.edx.org/ I think its a great way to learn. The one thing you won't get versus a "real" MBA program is group work. Group work at this level is a great learning tool and experience (don't think of undergrad group work when you're think of this). I think some distance programs have segments where you get togethers with other distance learners and complete group work. Sounds like you'll miss out on that.
I think for you, if you want to learn, then go for it but know that you won't get all the other stuff.
Do you need the degree for your job? Does your employer or potential employer require an actual masters degree for certain roles regardless of experience or other qualifications? That may be a consideration for you. Ill add that don't see many MBA grads include MBA on their business cards or email sig these days.