Let me explain how I manage FP↔Goods trades.
I actually use my own FPs/Goods value chart, which is not based on any unfair trade calculator you can find on the web. I find every single calculator out there doesn't have any clue at all about the true market value of goods or even the true production costs of refined goods. They all pretty much go only off the supply and coins costs for goods production, never factoring in land, population, side effects, 1-lane vs 2-lane roads, or even unrefined goods costs.
When I first came up with my own FP/Goods value chart, I actually started first with PE goods, because I had noticed that on all of the various FoE worlds on which I played the game, the player community has somewhat agreed on what a fair market value of FP/PE goods was, ranging between 20 to 25 FPs for 100 PE goods. The difference was usually if you were buying from a guild mate, or someone who was really a friend of yours (not just on your Friends List), or a player you didn't have much a of relationship with. In such transactions, it was generally accepted that the goods buyer would post a trade like the ratio shown below:
Have 50 <some crappy Bronze Age good> : Need 100 <some valuable PE good>
Keep in mind that the above is only an example trade Ratio; in practice, most actual trades are as large as possible so as to reduce the forge point costs the goods seller would incur by accepting a non-guild trade.
So for my value chart, I started first with the generally accepted value of PE goods and worked outward from there to complete the valuation of all other ages and eras. Here are the FPs-to-good ratios I came up with:
0 FPs/100 BA goods
1 FPs/100 IA goods
2 FPs/100 EMA goods
3 FPs/100 HMA goods
4 FPs/100 LMA goods
5 FPs/100 Col goods
10 FPs/100 Ind goods
20 FPs/100 PE goods
25 FPs/100 ME goods
30 FPs/100 PME goods
35 FPs/100 CE goods
40 FPs/100 TE goods
45 FPs/100 FE goods
50 FPs/100 AFE goods
55 FPs/100 OFE goods
Now in addition to using the FP valuations for the goods I'm selling, I also give my guild mates and close friends "FP Credits" for whatever goods they are trading back to me. Let me walk you through an example.
Example Situation within my guild
Let's say I have a Colonial Age guild mate who wants to construct the Arc.
I'm in FE, where I produce FE goods conventionally (with goods production buildings), and with quest rewards. To produce FE goods conventionally will cost me PME goods which are consumed as unrefined goods. But I'm well situated to handle my demand for the PME goods, because I have: Level 10 LoA (38 PME goods/24 hours), Level 9 StM (48 PME goods/24 hours), Level 10 FoD (34 PME goods/24 hours), and 7 Wishing Wells (7 x 29% x 20 PME goods/24 hours = 40.6 PME goods / 24 hours on average).
However, I also produce TE goods conventionally that consume ME goods as unrefined goods. But since TE goods are one age below my Town Hall, that means that I cannot rely on GBs/Wishing Wells to produce ME goods for me in order to sustain my TE goods goods production — so I either need to trade goods down several eras, or conventionally produce some ME goods myself. I actually produce ME goods myself. But ME goods also consume Colonial Age goods as unrefined goods. So I actually have a personal demand for CA goods.
So my Colonial Age guild mate can actually help me, while I help him. So this is what I have him do:
He post trades like this:
He has 200 <some CA good> : He needs 100 <some FE good>
For each 100 FE goods I sell him this way, he ends up owing me 35 FPs.
Why 35 FPs and not 45 FPs like my charts shows? Because, he traded me 200 CA goods, which on the chart is worth 2 x 5 FPs = 10 FPs in "FP credits" — I gave him credit for the goods he traded back to me in the exchange, because those goods are actually worth something.
As you can see on the valuation chart, Bronze Age goods are worthless because I cannot even donate them to my guild for GE or GvG, I will never personally use those goods, and I already have more than any new players who might join our guild will ever need for tech or GBs.