Before coming to these forums my method for deciding the site for Moai was simply calculating the water tiles and then checking if the city had some slowbuild production. Back then I clearly overvalued this wonder and nowadays build it later if at all. Moai coast tiles give the same yield as a grass forest plus the extra commerce, so I think these are tiles to be whipped away. Perhaps better way to decide a good Moai site would be counting the sea food tiles and lake tiles. These are tiles that will be worked almost all the time. But still it's 250 hammers without stone, with 5 seafood for example it would take about 50T to pay back, taking only the seafood tiles into account and not the possible growing onto sea tiles. When is it worth it? Definitely not in the expansion phase or when waging war.