What To Do When Competitors Discount Prices

An editorial stock agent tells me that he is trying to hold the line, or increase, the prices he charges for images because his providers tell him that their costs are increasing. Meanwhile, a competitor who is offering dramatically lower prices in an attempt to win customers has entered the market. As a result, the agent's providers are seeing poorer sales. He asks for advice as to what he should do? I’ll give some answers, but I also want to invite my readers to chime in with any thoughts they might have, or strategies that have worked for them.