Lee doesn't foresee the merger affecting market data pricing too much. "Whenever you have an 800-pound gorilla like Bloomberg in a market, it's tough for competitors to raise their prices," Lee says. Bloomberg is currently more expensive than the other two providers, which gives Thomson-Reuters some room to raise fees for certain services. But "in the end, this is all about market share grab," Lee points out. Each firm has specific areas of market strength: Bloomberg is well known in the fixed income market, although Thomson improved its fixed income capabilities by acquiring Tradeweb. Thomson's Thomson One wealth management platform also sells well. In foreign exchange, Reuters is strong; it has the second largest interbank platform globally. So "there are certain businesses that perhaps each could raise prices on, but in a fundamental competition between a Thomson-Reuters combined entity versus Bloomberg, I don’t think you’ll see prices being raised, I think if anything there will be more price competition," Lee says. He compares the two data providers to NASDAQ and NYSE -- when one exchange releases a new pricing fee, the other immediately undercuts it.

In a statement, Reuters laid out its case for why this merger will benefit customers, saying that customers will benefit from seamless access to richer content and broader capabilities and that the combined business will adopt the Reuter Trust Principles of integrity and independence.

But some industry observers are skeptical. “It remains to be seen if the Thomson/Reuters merger will benefit market data customers,” says Octavio Marenzi, CEO of Celent. “Users may benefit from the greater breadth of services that will hopefully come out of the combined company. Expanded services may provide customers with a viable alternative to Bloomberg.”

One thing that is certain is the more powerful Thomson-Reuters combination will narrow the array of market data choices for investment banks, hedge funds and brokerages. Thomson-Reuters will have a 34% share of the market and Bloomberg will have 33%. Smaller competitors like Dow Jones, which relies on Thomson and Reuters to deliver its market data feeds (and also faces an uncertain future if Rupert Murdoch buys the Wall Street Journal), will struggle to compete. While this could bring Wall Street firms closer to having a unified pipeline of market data, it could also be inhibiting. "There’s a danger of customers being held hostage," Lee points out, similar to the way some U.S. regions have only one cable company. "It’s easy in the sense that you don’t have to compare shops, but at the same time I feel like I’m getting robbed every month."

Another likelihood: heads will roll, most likely at both firms. The companies have promised they will find more than $500 million worth of annual cost savings within three years of completing the merger. "This could mean layoffs; hopefully it will be about integrating certain systems that overlap," Lee says. "We'll see if they're able to save $500 million, and through what means."