There are plenty of things you can say about Andre Iguodala. You can say he's one of the best all-around players in the league. You can say he is not a true superstar. You can say he's not a good shooter. You can say he's one of the best finishers in the game. There's some truth in all of those statements, but mostly they're simply opinions. Opinions are fine. That is not up for debate is whether Iguodala is overpaid, he simply is not.
This chart pretty much sums it up. What you're looking at is the top 21 players over the past 4 seasons sorted by win shares, their salaries this season and where their salaries rank on this list (not where their salaries rank league-wide).
You can read up on win shares here. Basically, it's a catch-all stat that attempts to translate tangible stats into wins produced for your team. Personally, I think Iguodala's value is actually higher than his win share total because most of his defensive contributions are not reflected, only his steals and blocks.
Take a look at the names on that list, Iguodala belongs there. He's #20 in win shares over the time period, and #18 in salary of the 21. The guy is not overpaid. There's more to this game than pure point-per-game measurements. If you insist on using nothing more than basic stats, you can look up all the players who have averaged 19 points, 5 boards and 5 assists per game over the past 4 seasons. There are three names on the list, Iguodala, Kobe and LeBron.
It would've been great if the Sixers could've locked him down for less money, but the fact of the matter is that Iguodala would've been an outright bargain at a lower figure. He and his agent fought for and got the contract he earned. The fact that the Sixers paid more than you would've liked to keep him does not mean he's overpaid. And as for the "bidding against yourself" argument, that's simply not the case either. Iguodala could've played for the qualifying offer last season and become an unrestricted free agent this past summer. Meaning, he'd probably be making more money than he is right now playing for the Thunder, Grizzlies or Trailblazers.