What you'd save at this point by buying Super Hornets would pay for a few more Typhoons and a lot of improvements to the Typhoon - conformals and vectored thrust &c.
The US is in a fix. It would make sense at this point to defer production of the B and C and focus on the A - because with three versions, the sheer number of engineering change requests is going to overwhelm the system, because the Navy has a Plan B, and because Marine STOVL jets are not as strategically important as the Marines think they are.
But if you do that, the C will eventually die as the USN keeps buying more F-18s, at which point the B becomes a really silly allocation of Navy resources - a vast procurement program to put six jets on nine or ten ships.
And everyone would rather not tackle the Marines head-on, or kick the Brits out of the program, not because the US does not want to hurt the Brits' feelings but because that could trigger the partner landslide.