I can’t figure out if this really happens because, if prices are determined by supply and demand,
Prices are not determined by supply and demand. Wether a sale takes place or not is determined by price.
Take a really simple case. There are 100 people who want a sandwhich. All 100 are willing to pay a dollar for a sandwhich, 99 are willing to even pay 2 dollars, 98 to even pay 3 dollars, and so on till one gu yis even willing topay 100 dolaars for a sandwhich, cause he is really rich and really hungry.
All that information about how many people are willing to pay how much is called “the supply curve”, because graphs on graph paper in economics books are called curves.
Whay is it that only one person is willing to pay 100 bucks for a sandwhich, and all 100 are willing to pay a dollar? That is because of personal valuation, Each of those hundred individuals has his own unique combination of wealth, hunger, other expenses, psychological and other neds, that go into deciding for him how much he is willing to pay. But whatever his final decision is, if the price goes past that limit he is willing to pay, he just won’t buy the sandwhich.
So if prices go up, less people are around who valuate the sandwhich at that higher price, and so less people will buy it.
and those willing to pay (or not) according to their subjective valorations,
“Subjective valuation” does not mean “Do I want a sandwhich at any price?” It means “What is the highest price am I willing to pay for a sandwhich today?”
then prices should not be moving if a there’s a change in taxes or costs
Prices are made buy the sandwhich maker, who tries to find a price that will give him the maximum profit. He knows if he sells for cheap, he will sell more sanwhiches, but will make less profit on each one. If he sells for more, he will sell less sandwhiches but will rake in more money for every sandwhich.
If he is taxed, then he has to rethink his strategy. “I am now making less profit per sanwhich than I used to. Maybe I should raise the price a bit, because although less people will buy it now, I will get some of the profit back that the tax has eaten up on the ones that I do sell.”
If his costs go down, and he is making more profit per sandwhich, he also rethinks., Maybe it’s worth selling at the older lesser profit [cheaper] to get more people to buy."
because they are not fixed to those factors, but to subjective valorations and supply and demand