I must disagree with this statement. A L1 Crystal Lighthouse would currently provide me with 519 goods per chest. At 3 chests per day that totals 1557. My elixir factory is L15 taking up a 4x5 space. I have max boosts for that and a L1 Mountain Halls. The production from my elixir factory is 1500 every 3 hours. I tend to complete that production 6 times per day, making the total output per day 9000 elixir.As can be seen from the graph obtaining one of your 3 rewards is as efficienct as one of your factories or just below, if you obtain 2 or all 3 reward chests your efficiency is well above that of a single factory without allowing for Magical Manufacturing spells.
My crystal (16 squares) and steel (18 squares) do not have max boost yet. They are both L19 and produce 1498 and 1414 respectively for each 3 hours.
I think in your graphic you failed to account for boosts. Anyone that has developed enough to be able to build the CL/BS will likely have at least a 300% boost and most will probably have 500% or higher.