Isn't one of the points of containers is that you can have many small containers that run 1 application? If that's the case pricing per-container seems... very expensive.
You know, initially I was wondering what the added value (except for abstracting away the raw OS management => automated management) was compared to DO until I saw that you're running with them ;)
Good luck though! Sounds like a good approach although I'm not sure whether charging twice what DO is charging you is going to work out.