One person left because he wanted to be paid significantly more than his work was worth at the time (according to me, my cofounder, and the 5 people we put in charge of a "pay team" to resolve this). He left, and it was better for him - he took a year off, decided actually the problem was he wanted to be doing charitable work and the money was a way to make up for that gap. He's now working at a charity.

I see it as a loss, but I'm not sure it was an avoidable loss.

Nobody else left because of pay transparency. Before we got our feedback in order, some people left because of feedback about their work, which only came after a round of pay changes, which made it clear to them that they were not doing work that was valued by the company. In those cases it would have been much better for everyone if we had delivered that feedback much more quickly! We're better at this now.