Around my parts the price of gasoline jumped basically 10% last Friday. How is it that EVERY gas station raised their prices the same amount at basically the same time? If a lot of other industries tried to raise their price 10% over night with very little justification for why it was happening consumers would tell them to take a hike. If a burger joint jacks up their price I can go to a different burger joint or not buy a burger at all.
Good questions. The answer is in understanding how supply and demand operate in a practical sense in a free market.
Crucial to this understanding is knowing that the only real factor that makes people decide where to buy gasoline is the price. For 99% of customers there is no difference between Brands A, B, C, D, E and F except for the price, and that's why every gas station advertises the price on the GIANT sign out front. This makes for a very competitive market and the owners are always monitoring everything that affects their cost, such as cost of oil, change in weather, shut down at a refinery, etc.. Because they've gotten good at reading how customers react to price changes they can set new prices overnight to get pretty close to what the market will bear while still making their profit margin.
That's why when a cold snap hits most of the country, gas prices will go up .10 a gallon within a day or two. They won't all go up the same amount, because a few stations will be a bit cheaper and a few will be a bit more expensive, but they will all be fluctuating pretty close to a median price and the owners will keep fiddling with that price as they gauge what customer reaction is in their local market. Then the next thing happens to affect their cost, either up or down, and they adjust their prices accordingly.
But every bit of this is geared toward making a certain profit margin which has nothing to do with what the companies "want", it's just
what is. They know that the 8% is what the market will bear and they can't operate outside of that.
To put it another way, suppose that there are 10 gas stations in town and 9 of them respond to a cold snap by raising their prices .10 while 1 station keeps their prices the same. That station will lose money. Not just make less money, but actually lose money. The same thing would happen to a station that decided to raise its price by .20 when everyone else only raised it .10. Nobody would buy gas from them and they'd have no revenue.
The reality is that the price of gasoline is set by the people who fill up their vehicles by virtue of the decisions they make in where to buy gasoline and how much they'll buy there.