Here (link) is an interesting story from The Economist which discusses huge price disparities between French and German retailers. For example, a basket of almost identical durable goods costs 30 percent more in France than in Germany.
The article reports that in many places in France there are local retail monopolies protected against domestic and foreign competition. There is also no free negotiation with suppliers, the sale of non-prescription drugs is prohibited, and the consumers do not support the new law that would deregulate the retail market to liberalize entry conditions and enforce competitive mechanism.
There is a well-known fact from microeconomic theory that consumer demand curve for monopoly firm equals average revenue of the monopoly firm and that monopoly firm will never like rigid or completely elastic demand but the elasticity of demand that will be equal to 1, given the point of the maximum profit taken by the monopoly firm. Hence, the price charged by the monopolist is P = MC/1+(1/Ex,px) which means that greater monopoly power leads to higher mark-ups. And also, the allocative inefficiency of the monopoly means that firm will set the price at the point where marginal revenue and marginal cost are crossed. Hence, higher prices and quantity regulation maximize the profit of the monopoly firm but consumers face a significant welfare loss.
In France, however, only 42 percent of the respondents favored more competitive retail market while 85 percent favored sales tax cuts and 72 percent prefered the rise in the minimum wage. Competitive market is always the only way to break the rigidity and monopoly position of the firm inparticular markets. For example, if there would be sales tax cut, that would not change the structure of the market but it would have an effect on the price elasticity of demand and since a local monopoly firm would face changes in the composition of the local demand, a tax cut would ease the prices but would still give local monopoly firms incentives to impose the mark-up. A rise in the minimum wage is a fallacy that, empirically, results in the rise of the unemployment and further labor market rigidity that hinders the growth of real productivity, decreases job growth and does not stimulate the real increase in purchasing power parity since higher prices, charged by firms to cover-up the loss from minimum wage, discourage the increase in purchasing power that is not linked to real productivity growth.