Free agents are overpaid as a group because of baseball's service time structure, and this kind of analysis is always going to make the group look bad due to a few bad eggs. It's particularly bad with relievers and WAR, because great relief seasons often only tally 1 WAR anyway. Looking at your list, the first guy (Affeldt) had an average season, a stellar season, a postseason not included at all in your tally (with Affeldt pitching 11 games/innings without allowing a run or an inherited run to score), and a bad final season when they finished 8 games out of the playoffs anyway. Do the Giants really think they "lost" $24.6 million on that transaction? Also, Cameron concludes that you might as well sign minor league free agents, but he doesn't actually perform any analysis of minor league free agent relievers. Getting a minor league free agent reliever that costs nothing and produces nothing indeed seems better than a negative performance on paper, but what are the odds you actually get a plus performance like Grilli or Soria from a minor league free agent, or even a mixed bag like Affeldt? It only really matters if you think the money could have been invested elsewhere, and given the extremely modest amounts of money we're talking about here relative to MLB payrolls, that's far from clear. $6 mil AAV over 2-3 years is very difficult to better allocate.