I maintained a POS for a large retail chain - and the variety of transactions that it could handle was far narrower and less subtle than the type of trades that

I maintained a POS for a large retail chain - and the variety of transactions that it could handle was far narrower and less subtle than the type of trades that I witnessed working at a weekend open air market. At the market there was all sorts of bartering and swapping and deal making - my “business analyst” brain recognised that to model all the “transactions” occurring at a typical market would be super complex. However… the large retail chain should not support subtle/overlapping transactions of that sort- not because it’s too complex to model, even if it was free to model it, make the software track it — the reason the retail chain would avoid it is: profit margin. You do profitable things, you do them a lot, and you don’t pay the opportunity cost of doing less profitable things. That’s the open secret of successful retail. And small businesses everywhere do not internalise this.