Fuel efficiency is not isolated factor, you need to put into the specific system, like user case. For example, the Cessna 172 is more on fuel efficiency for carrying light but high value stuff to cross border between US and Mexico, than bigger plane.
If you have basic sense about economics, you should know the
Price Tag is outcome of a total system. The system contains of production rate, labor cost, government subisidies, loan rate of bank, the desgin of route ... fuel efficiency is just one parameter of the whole system.
So your conclusion is very superficial only based on fuel efficiency, if so the world only needs one automobile company like Toyota before the EV era, and Toyota only needs to make one type called Camry.
View attachment 208535
This is the file from China Aviation Administration, it asked all the airports give the 1st priority on airport traffic control, landing priority, best route and height in the air ...
All these factors will make C919 profitble and if there are 2000 orders, there will be a million high payment jobs inside and outside of China, this is how Chinese EV industry got started it's the integrated advantage, you may never understand.
So we really don't care too much about fuel efficiency alone.
BTW, for E-195 or SSJ-100, E-195 is not the same class of C919, just like DJI is not the same class of E195; for SSJ100, i will ignore it before the supply chain resumes, just like we don't talk MRJ anymore.