Price Point
Yes I agree with you that it's all about the price point and comparing that price to the alternatives.
Further I entirely agree buying a $65 million F-35A is a much better buy than a $60 million SH or even the $50 million that the USN is being offered for a multi year buy.
It probably makes sense to purchase $100 million F-35A's instead of most alternatives (although at this price I think a 1/3 cost A-10 replacement makes more sense and if you actually do need air superiority aircraft than a $140 F-22 might be worth a second look at this price point); however, at some point the price of the F-35 rises to a certain point where it tips over from making economic sense in favor of the the alternatives.
The concern with the program now is that we may be on a trajectory where we pass this point or that indeed we have already passed it.
The point regarding the SH for the USN vs the F-35C is very important. At $50 million for a new F/A-18E/F (multi year contract) it makes little sense to spend $26 million to SLEP older and less capable F/A-18's that gain up to 1,400 additional flight hours when a new SH is good for 6,000+ hours. Furthermore, at some point north of $100 million (certainly north of $150 million) it does not make sense to purchase the F-35C vs the SH. There is also the UCAS-D/X-47B follow on aircraft that will have longer range and greater loiter time with a similar internal weapons load.
It's not clear we actually know the alternatives to a SLEP for the USAF even if only to provide gap filling aircraft before delayed introduction of F-35A. Nor do I believe there is any study regarding an F-16 SLEP much less data to compare to new build alternative. In any case I'm not suggesting the USAF start operating the SH; however, the current offered multi year price could be leveraged toward bids for alternatives.
The problem is that all we hear is that there is no alternative to the F-35A for the USAF when in fact it keeps getting delayed. At some point, and in the view of many we've passed this point, the USAF must deal with a significant fighter shortfall by extending the life of existing aircraft or buying new aircraft or a combination of both. This is the elephant in the room because money for any new fighter will be seen as less money for F-35A within the USAF budget. It's an unsustainable position- especially given further delays in JSF.
You may have a point comparing acquisition cost of the F-35C with the SH, however to the air forces it doesn't make sense to buy $60m super hornets instead of $65m F-35A. $60m is probably the cheapest fly-away you would be able to manufacture a SH to in today's dollars.
SLEPs including structural zeroing are notoriously expensive as you point out.