So you know the market prices on all the worlds within one or two jumps of this one, even though you are in the wilderness and there is no polity moving such data from world to world? Even the Imperium only moves market data regularly between worlds on the xboat route.
Again, where do you get the knowledge of the markets way beyond your original empire? Who trades the data? How up to date is it?
Until you arrive at that city and find it full of multistory pig farms...
I disagree most strongly, that is not what broker skill or brokerage is by any understanding of the word, a broker is a middle man who knows both sides in the deal, they make money by getting the best value and taking a cut, They get the best value because they understand the local market forces and interested parties. I fail to see how someone from a sector away arriving on a wilderness world will have that sort of knowledge of the markets on that world.
No, a broker is an intermediary between two parties, with understanding of both sides. You are describing haggling, trading, not brokerage.
And you need to know those and those of the worlds you wish to trade with.
The skill shouldn't exist as written.
There used to be a much better named Trader skill...
Oh, I thought we were talking about the Broker Skill is it is used in the MGT2. All you say may be true for an actual "Broker" but I think that specific word has different meanings depending on context. They were certainly somewhere in the middle of the supplier and the end user, but what exactly the difference between a broker and a trader is open to interpretation. You could argue that a broker never actually owns the goods they just negotiate transfers of goods between two other parties, but that is not the description of the Broker skill since it is about the skill of negotiating, not the facts of ownership.
How do I know the price of goods? Well I can see it right there on the tables on page 244 and 245. If you are talking some scenario where you are buying or selling goods other than appear in that table or where the prices are different to those then I am also inclined to agree with you, how would you know, as a player or a character. As a player I can see I rolled well, maybe my character has a good feeling about this deal. Or are you asking the meta question on how skills translate to actual character actions. I would say that is too large a question for me to worry about. There is a game mechanic and I leverage it. I don't have time to actually study every field of science to understand what that science roll actually means. I just know that if I succeed in the roll my character does.
I would find out the prices of goods where I hadn't been before the same way I would do it IRL for a foreign country. I'd scour the data nets for clues. If the local news is full of adverts for goods, then I know the retail prices. I can look at the prices in the local Starport, or markets. Those are prices people are willing to pay. I could ask some locals what the latest fashion is. I can probably infer from all that a sensible margin. Some prices might be inflated (I might fail my skill check).
Even if the current stock prices were not being moved around by the polity, unless the economy was in a complete spiral (which is possible) then I'd expect retail prices to remain fairly stable. I am not buying commodities, I am buying goods. A planet that has trade probably has visitors and people who travel all these people leave breadcrumbs. Tourist come back raving about the local wine or how expensive meat is there. There might be a merchant venturers guild where we can compare notes, we might be in friendly competition and the person getting the best deal of the week buys the drinks.
In the worst case don't think I would zoom off to a new universe completely without preparation, buy stuff at random and them zoom to another and try to sell them. I'd do what everyone else does, identify an Agri planet buy goods at the Star port for the lowest price I could and then find am Industrial planet to sell them at the best price I could get for them. A single iteration of this would tell me most of what I need to know.
I am not sure changing the name of a specific skill makes any difference (or the Spanish printing of the rule book would be a completely different play experience). If you however choose to infer a game mechanic that doesn't exist because of your interpretation of what a single word means then I'll let myself out here.