The Harden you see right now wouldn't be the same Harden if he stayed in OKC (this is what people must understand), in terms of the production/output/impact he has. He would be at most a 18 ppg scorer with playmaking - that's not worth $60m on a team like OKC. Harden is worth that much in general, but not on a team which has two elite perimeter players already - there's not enough areas in which he can contribute to warrant that sort of money at the time (it would be different if he was a center who could protect the rim and/or pound the glass and give them an advantage on the block).
y'all are legit fools if you think their current payroll means fukk all for what happened back then. they didn't pay up because they didn't want to pay that much for a third man and now they did as they feel the heat of durant's pending free agency. ignoring the context of why they're paying in the tax now and why they didn't back then is stupid.
I don't think Harden would be a 28/5/5 guy, but he would be better than he was and a lot better of a third option than Kanter is now(Kanter barely gets 20 MPG). Harden would give them more value for less money and he was worth 60 million to them then and would be now. He also would have made a huge difference when those injuries happened and would have made big strides in his development during that time as well(assuming they still happen). Harden would have given them another playmaker, something they desperately need as one of the teams with the least amount of passes in the league. They were a better team with him than they were without him, the biggest question mark would be if Westbrook ever becomes the playmaker he is now if Harden stayed as he wouldn't need to have to do as much as he does now. Again that's not necessarily a bad thing as they need more playmakers.