The way some people are making it sound, we shouldn't have even re-signed Horford to 60/3 years. Seriously, if he's really that broken down and old how can you justify paying him anything 20 mil and above/year?
They're going for a title. All they're doing is paying an extra 8 million a year and guaranteed 15 in the fourth year. To a team that's going for it, that extra amount is not a dealbreaker. If you want to poke holes in a lot of the deals made this summer, you easily could in many of them. Durant is coming off a major injury and won't play next season. Just a year ago Kyrie's knees were a big deal. Paul George dropped off late last season due to his shoulder injuries. Kawhi is only a year recovered from a mysterious injury that put him on a 60 game load-management plan in the regular season. Anthony Davis has been injury prone his entire career.
My point is just that, when you're going for it, you can afford to make "bad" deals to push yourself over the top. Every deal needs to be seen in the proper context.