It's not so much whether it can be subjectively qualified as "expensive" as what is given up or delayed in order to build it. Everything has a cost. Even if you simply have the NE build units or Research, that's something you have to give up. That's an issue we haven't really discussed. For example, a parallel SE can spread out wonder builds to multiple cities, and make effective use of them. A serial SE, to maximize GPP production, has to delay wonder builds (i.e., has to queue them up) and this both risks losing the wonder to an AI and also delays getting the benefit of the wonder. This is where you say yes but this pollutes GPP type in the GP farm. Yes, and that is a reason why you may desire to build a wonder in a city you never want a GP from, period. Nevertheless, that is lost GPP and perhaps a tiny % risk of pollution is worth it to increase GPP production. Or, perhaps you're doing a golden age strat and thus any GP is put to good use. Or several other scenarios. Anyway. A parallel SE can focus different cities on different types of GP, and build appropriate wonders in each. GPP pollution can be controlled as desired, either to eliminate it or to choose to intentionally place it in certain cities. i.e., one city with 30% pollution but will only produce 1-2 GP over the course of the game may be more desirable than having a GP farm with 7% pollution and producing 15 GP over the course of the game. Yeah, that's certainly a big affecting factor. Choice of parallel or serial SE as part of overall game plan is part and parcel with what civics are desired to be run. No I think you misunderstood... I must have not said it clearly enough. Say in a parallel SE you have a city specifically producing prophets (for shrines) at the same time you have a GP farm. Delaying production of multiple prophets can mean a HUGE amount of lost gold. My usual problem is that I often HAVE TO HAVE a specific guy, say a merchant to found sushi. I have to "turn off" my GP farm (which is producing a huge chunk of my total empire reserach) in order to spit out that merchant. Well good I sparked a discussion then. I myself like game variety and experimenting different strats... I think it keeps the game fresh and interesting. Which is why I keep playing after what 3 years now?