For example PE to CE the FTC says 2:1 if fair, I am saying it is ripping off the higher age player.
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However, if I gave you 100 Bionics for 200 Asbestos I lose out. Why?
Each unit of bionics I trade to you has 1 unit of Asbestos in it in order to be produced.
You give me 200 asbestos, I give you 100 Bionics but I also "give" back to you 100 units of Asbestos it cost to make my 100 units.
The trade rate is therefore 1:1
200 Asbestos requires 8000 Supplies and 8000 Coins to produce (after the one-time cost of the building).
100 Bionics requires 3200 Supplies and 3200 Coins, plus 100 Asbestos (which in turn costed 4000 Supplies and 4000 Coins) - again, after the one-time costs of the buildings.
Therefore the total Supply/Coin cost of 100 Bionics is 7200/7200 as opposed to the 8000/8000 cost of the 200 Asbestos.
So if you're getting 200 Asbestos for 100 Bionics, you're actually making a slight profit. 800 Supplies and 800 Coins worth.
The one-time costs of buildings is negligible, relative to the amount of goods you'll eventually be producing. After all, you're going to be producing a lot (if not most) of the goods for yourself - not to trade, but to use to build GBs and unlock Techs, and negotiate in the Map and the GE, and to donate to your Guild.
I also generally don't consider the sizes of the buildings as relevant to trade value because you get all that space back when you eventually remove the building (not to mention a lot of the coins and supplies you used to build it). If you happen to get the Stone boost in Bronze Age, well unlucky you - you need to build a 4x4 building instead of a 3x3 building. But soon you'll be in a later age and you won't need that Stone Mason anymore, and you'll get back the entire 4x4 space to use for your newer buildings. Maybe in Iron Age, you'll get lucky and get the Iron boost instead of the Ebony boost, and you'll only need a 3x3 building instead of a 4x4. Or you'll get Honey instead of Granite in EMA, etc.
I use a "trade calculator" (actually a spreadsheet I created myself, because some of the online calculators are either inaccurate or not updated). But it's really only as a general guideline. The Coin/Supply cost ratio between OF and AF, for example, is 129:117. I might offer 129 Nanowire for 117 Plankton. Or vice versa. But because the game currently ends at OF, there is a shortage of AF goods relative to OF, so if I really need Nanowire badly, I might offer 100 Plankton for 100 Nanowires. Or if I think others are in dire need of Nanowires, I might ask for 100 Plankton in exchange for 100 Nanowires.
I find it hard to imagine a scenario where I am so desperate that I would offer 200 AF goods for 100 OF goods. But if there's a sucker out there offering 200 AF goods for 100 OF goods, I won't pass that up!
129:117 is IMO, reasonably close to 1:1 (or 100:100), but it's too far from 2:1 (200:100) for my liking.
Anyway, the bottom line is: Caveat Emptor! If you don't like the trade, don't take it. It's not other players' responsibility to make sure you don't get ripped off. Although if they're in your guild, you really shouldn't be ripping them off (nor they, you).