More On Fixing The Trading Game

1) The LBB2 spec trade rules are meant to model a particular corner of merchant trade, not an entire interstellar economy.
2) If goods can be bought and sold profitably on a given world, that market will be controlled by locals for the most part, and will not likely enjoy wide fluctuations in price. Once a price is determined for a specific lot of cargo on a specific world, its price is fixed. (Different lots of the same class of cargo may vary.) This means that if you want a better price for a cargo than you've got on planet X, well, you HAVE to bring it to a different market.
3) The idea is this: if product X is available very cheaply onworld, there's a reason for it: it can't sell well here.
4) Onworld trade certainly will happen: but Travellers won't have access to it normally. They're outsiders, and local trade will be the province of insiders. Breaking into that trade would run afoul of local authorities and merchants (and could be the source of adventure in itself.) But chances are, the profits won't approach what could be had by the canny interstellar merchant - which is why we take out the multimillion-credit mortgages.