I ran an all-too-brief Traveller campaign about eight years ago, a bog-standard space-merchants-with-a-mortgaged-free-trader-and-a-mountain-of-debt. As part of my prep, I worked on a table of events associated with speculative trading, to use in conjunction with the Actual Value table in the rules for trading.
For those of you unfamiliar with Traveller, merchants can transport other people's goods, but at best that will keep you living on the edge of a potential repo. Speculation - buying your own cargo on one planet and selling it on another- is riskier but offers by far the best potential for profit. The Actual Value table is consulted when buying and selling, and provides a percentage modifier to the base price of the cargo; if the base price of a ton of wheat is 500 ImpCr, and the Actual Value table result is 80%, you can purchase it as 400 ImpCr per ton.
What I wanted for my campaign was an additional table, that provided modifiers to the Actual Value roll, stuff like, 'Market saturated, - 2 ,' or, 'Sudden demand, + 1,' to add flavor to the results. I worked out a d6, d6 table of results, but it still seemed bland to me, so I and showed it to a buddy of mine. He ran his Traveller campaign for something like fifteen or sixteen years at that point, and he regularly had far more players looking for seats around his table then he did chairs to accommodate them. I knew his critique would be helpful.
He looked over the table, then put it aside and grabbed a pair of six-sided dice. 'You have a cargo of cybernetic parts and you're on [planet name], an agricultural world, jump-three from the industrial world of [planet name]' he said, tossing the dice on the kitchen table. A three. 'Fifty percent,' he continued - there was no need for him to look up the Actual Value chart, as he knew it by heart - 'an Oberlindes Lines bulk carrier arrived a week ago, and the market is flooded.' He picked up the dice again, and tossed them once more - a ten. 'One hundred thirty percent. Looks like those LSP robotic harvesters that arrived six months ago are acting up, and the replacement parts haven't arrived yet, so there's a price bump.' Another roll - a twelve. 'One hundred seventy percent. Not only is demand high for parts for those harvesters, your broker just found a loophole in the tariff code.' He tossed the dice a couple more times, each time improvising an event from the memorised table of generic percentages.
'It's already in there,' he finished with a smile.