The USAF's reversal on buying F-15's...is it about cost or capability?

Thanks to Mobius for the link!

via The Diplomat.

Interestingly, a senior U.S. Air Force official revealed that “the last time we looked, this was more expensive than buying F-35s in bulk.” However, he confirmed that the option of purchasing 72 aircraft is nevertheless still on the table.
The U.S. Air Force has already asked for cost estimates on procuring new F-15s and life-extension/upgrade options. “Also under consideration is a plan to augment U.S. Air Force electronic attack capabilities by fitting some F-15Es with a version of the Raytheon Next Generation Jammer pod,” the article states.
Overall, the Pentagon is planning to procure 2,457 aircraft by 2038. Total acquisition costs are estimated at over $400 billion making it the U.S. military’s most expensive acquisition program. Operation and support costs throughout the aircraft’s lifetime are estimated at over a $1 trillion.

Here.

We have to ask a serious question.  Is this about cost or capability?  Note that the unnamed USAF official said that the last time he looked buying the F-15 was more expensive.  Of course he could be talking about the fairytale cost estimates that the program has put out or he could be actual and factual.  We don't know.

What we do know is this.  The USAF, USMC and USN have talked about the F-35 acting as a sensor node.  Additionally the USN has always planned on using the F-35 in conjunction with the Super Hornet with the Lightning 2 performing the electronic  attack/ISR mission.  In essence they talked about the plane clearing the way.

Now in this article we not only hear about buying F-15's but also fitting them with Next Generation Jammer Pods.

The F-35 was suppose to render the EA-18Gs obsolete.

So again.  What gives?  Is this about cost or capability?