I know its not a decision, which is my point, why it would be pointless to incorporate the decisionless gold maintenance in this case, Their is no point to it, and that is a fact. The Strategic Decision cost can not be obtained on gold buildings from gold maintenance.
Yes you SHOULD be asking yourself if its worth building, gold maintenance will not do this job, hence it is pointless.
In addition, if you are creating values, you will create both the original and the maintenance and the result, which is fine, until the result becomes singular, i.e "2X - X = X" So the creation of the calculation becomes a muted point, you may as well of created to start existing at X. Maintenance in this case is pointless. Because it can be replaced by simply not inventing it in the first place. Inventing 10 calculations to get to the same result as 1 calculation is a pointless waste of time. E.g "(10X / 2) -2X -2X = X net effectiveness of building" as apposed to simply having "X effectiveness of building". This is simple, maths, logical and factual, the simplest calculation should be used for that exact purpose.
The reason to have Maintenance is when the cost can't be simplified, when their is a CHOICE, i.e "2Y - X" Then you have to choose what is more important to you, 2Y or X.
The reason why "+X% - X" is not a choice is because either X>0 or X<0, if X>0, the "Choice" will always be Yes, if X<0 the "Choice" will always be No. All you will be doing is forcing an uneccesary calculation and a predicted resulting "choice", which is no choice at all. If your playing to maximise profit, which means, playing to win the game, then thier is no choice. You will do the predicted action, where as, X or Y is entirely variable, completely depending on what type of victory your going for and what would be more useful in getting it. A Choice if you will.
IF you WANT a Maintenance Decision Cost on Gold Producing Buildings then this cost must not be in gold, it can be in science or culture or Strategic Resources or anything really, accept the bonus the building gives, otherwise the Maintenance which is inserted to give "Choice" will give none.