Ok, firstly i'd like to say, that i appreciate the events that Inno put on for us, and i do appreciate the 'free' buildings.
But calling them 'free' isn't really acurate is it. Completing these quest runs, does take a lot of time and effort from the players...and in the case of the big events, real money too! At least if you want the 3rd building in the big events.
Bearing that in mind, the rewards really do have to be worth it. Especially if you expect us to build non-boosted manufactories.
I'm in Chapter 8 at the moment, and the reward for part 2 of this event is 250/490 pop/culture 4x4. Compare that to The Well of Floating Islands from the beginning of Chapter 2 (yes CHAPTER 2) which is 400/440 pop/culture 4x3. Do you think that's worth even the slightest bit of effort from me? I'm gonna say thankyou, but no thankyou
I appreciate that The Well of Floating Islands is a diamond building, but i buy diamonds, so any event reward has to be on par or at least close to a diamond building.
Now.....if there was the possibility to upgrade past event buildings to your current chapter either by paying diamonds or some other way, i'd totally go for it! The mana could probably come in handy in later chapters. The supplies it offers would probably be useful in lower chapters, but for me, in this chapter, no. So you seem to have missed out on any incentive for the middle level players with this reward.
I'm not even going to go into the individual quest rewards (the instants) cause i'm honestly gobsmacked by them. Maybe you should consider making those tiered also to make them worth it.
My personal preference when it comes to events, is quality over quantity.