Price transparency can in some settings facilitate tacit collusion by enabling firms to see what other firms are charging, and hence easily detect any deviation from agreed-upon high prices.
Policing the digital cartels, by David J Lynch in Financial Times
As an example, he cites a German software application that tracks petrol-pump prices. Preliminary results suggest that the app discourages price-cutting by retailers, keeping prices higher than they otherwise would have been. As the algorithm instantly detects a petrol station price cut, allowing competitors to match the new price before consumers can shift to the discounter, there is no incentive for any vendor to cut in the first place.