Under normal conditions, if one company increases their price then buyers will find an alternative.
When all the companies increase the price at the same time then there are no alternatives. Customers become acclimated to the new price.
One reason is buyers may only consider alternatives when prices increase.
Under normal conditions, if one company increases their price then buyers will find an alternative.
When all the companies increase the price at the same time then there are no alternatives. Customers become acclimated to the new price.