[Think of all the choices that have been eliminated. That's why today a station on every corner of the intersection sells at the same price.]
The reason that gas sells for nearly same amount is that it is nearly the same product from one station to the next and there is no practical difference to the consumer. Since they all advertise their price on large signs, any store which sells for a lower price gets more customers. The result is that all area stores quickly equalize prices to the lowest amount which is still high enough to make a profit.
"The reason that gas sells for nearly same amount is that it is nearly the same product from one station to the next and there is no practical difference to the consumer. Since they all advertise their price on large signs, any store which sells for a lower price gets more customers. The result is that all area stores quickly equalize prices to the lowest amount which is still high enough to make a profit."
You've just defined price fixing.