Generally, you work out a deal with someone that has the goods. There is normally, though not always, a donation of FPs from you to a GB of the person you are dealing with. There is also the actual goods trading, which can be, as you say, your current age goods for the higher era goods, or lower era goods (Bronze, Iron, EMA...) for the higher era goods. What the person providing you with the goods is really after is the FPs, so the goods you trade are inconsequential to them, or should be. Now, normally you will work out with the other player how many FPs you will donate for the number of goods you receive. You will receive 1-3 goods per FP from most players.
However, when someone offers a "package" deal, they usually do it for a specified number of FPs, which is generally lower than if you were doing a regular deal with someone. The specific deal I saw was 345 FPs for either a Traz or Chateau goods package. The package would be the quantity of each of the 5 goods necessary to build the Traz or Chateau.