@lotherio I don't mean to be attacking you here, so I apologize if it seems like it, but this also seems unecessarily defensive.
The systems were not posted.
While its obvious players could interact with NPCs, the context, rules, etc for doing so were not available. I'm not accusing you of giving a player special information, but rather suggesting that when they contacted you, you presumably communicated to tell them how their +request would work or what choices they had. Other people didn't have that info. Even as of these very posts, we're getting new information: for instance I'd assumed it was more of a trade off (get the high prestige NPC, but pay for it), where now it sounds very win-win (get the high prestige NPC, they pay for themselves and then some).
The game is very new, so we expect to learn things as we go, but its also pretty clear you have some things detailed out more than we're aware, and the clarity is important.
The trade - your one gain to get the commodity from another house to pay debt means break even. This is intentional. Its basically using any gain your house has to pay any debt incurred but asking players to rp the exchange versus staff just accepting the exchange. You're right 1 commodity credit and one commodity debt balances to zero. The PrP doesn't help with house interaction as a quick write off and is a more viable option mechanically I agree seeing it play out.
So I think this is a place to focus on looking at some new mechanics.
As it stands, the whole income rolls aren't very satisfying. First, its a flat out punishment for a bad roll, no strategy, despite everyone having the same stats. Then it encourages an insular PrP, that while it might be fun the first time around... I'm willing to bet will quickly turn into 'busy work' as more of these rolls fail. This isn't a personal negative, just a statement that this mechanic that doesn't seem like it's working to promote interactive stories.