Depends what and where you're trading. And yes, it's a bit simplified, but since it already has more complexity than most people are aware of, there's no point in it being much more detailed until people are making use of what there already is.Except that 10 minutes later the demand refreshes like nothing happened. Why isn't the demand gone? Or if you say that they need a fresh batch of items, why aren't the prices different? It's very artificial.
This is a fairly small station, though, with a relatively low number of NLWs demanded, so the demand recovery rate is only about 2t in every 10 minute refresh. It took most of a day for the market to fully absorb that really big sale - and it would take over 4 days to recover if someone brought in a couple of full T-9s. But there are lots of goods and markets where the volumes are much higher, and a 10 minute refresh can stick another few hundred tonnes of demand in.
In practice, it's not even really noticeable here - there are only eight NLW sales over the two weeks, and only one of those occurs quickly enough that the market hasn't fully recovered from the previous sale, and then only just. So all this supply and demand activity is going on in the background, but no-one notices any actual effect on their prices.
With over 150 trade goods and about 60,000 markets, there are nowhere near enough traders to change that for most goods. A significant reduction in the total demand tonnage (about 475 billion tonnes) and in the rate at which met demand recovers would be needed to change that.
 There's a lot more data available if you want, but I've trimmed it to a date range where there's no BGS state changes going on to show the supply/demand effects more clearly.