The argument is more likely "Harden should have accepted what the Thunder could afford". The cap is 58 mm. Durant/Westbrook make a combined 31.2 mm. Harden's new contract is for 16 mm per, which would put the Thunder at 47 mm in 2011-2012. That leaves them 11 million to fill out the roster, and Ibaka is getting paid 12 mm per year starting in 2012-2013. With their annual salary bumps, that puts the Thunder over 3 million over the cap with only 4 players. The smallest amount of money they can pay (league minimum for rookies) is 500K a pop, which means that filling out a 12 man roster with rookies would put them 7 mm over the cap (65 mm).
Figure that you're realistically going to end up with at least 12 million invested in the "non-big 4" part of the roster and they are 3 mm into the luxury tax... and that assumes that they get rid of Perkins 7 mm per and don't pick up any other posts with a pulse, because decent posts start at 4 mm and go up fast.
Their options were to
lose Ibaka, who is slated to get a very reasonable 12 mm, a premier shotblocker and developing offensive player
lose Durant (no)
lose Westbrook
completely gut their roster outside of Durant, Westbrook, Hardin, and Ibaka, probably only pay 8-9 people and half of them would be rookies or spares
lose Harden
As combo slasher guards, Harden and Westbrook are the closest things to redundant on that list. Do you invest 30 mm in PG/SG and erase your depth or defense, or do you trade the more expensive of your two guards for a quality role player (whose contract is up after this season), a prospect with potential, 3 draft picks, and payroll flexibility?
[This message has been edited by Ulrich (edited 11/2/2012 9:14a).]