Look, very few players in the entire NBA are actually worth thirty million a year. The number is in the single digits. However, Kevin Love is a perennial All-Star (injuries have really been the only reason he has five appearances instead of eight or so), and All-Stars get paid max money. Max money right now happens to be around thirty million, give or take about five million depending on years in the league.
Further, Love actually took less than the max to stay here. He left eight million on the table, which may not be a ton in the grand scheme of things, but how often is an All-Star player willing to leave money on the table to stay with the Cavs? LeBron sure as shit wasn't willing to do it, and it's probably going to ensure he retires with three titles instead of four or more.
So while I agree that, on paper, thirty million for Love is an overpay, Love was going to get that money from someone next summer when half the teams in the league will have a lot of cap space and there are probably only going to be a handful of star-caliber players that actually change teams. Hell, he probably would have gotten a full four year max from someone instead of losing out on eight million.