The future of an in-debt Navy.
Since the USMC has shown the idea that the F-35B can do a short take-off and vertical landing, the Navy now has to worry.
No matter that the F-35 has unfinished mission systems, is yet to drop a weapon or get qualified in an actual go-to-war squadron; with a known price.
The USMC has also claimed that their flat-tops are carriers; feeble minded fantasy but marketing is everything. This is good news to a Congress that is trying to pay for DOD largess and has no realistic way to pay for large traditional carrier groups. They are talking about cutting big carriers and not making any more fifteen billion dollar replacements.
So in that sense, even if it doesn't work much, the F-35B will be cheaper for America; as long as you don't count the expense of losing a major war.
The USMC amphib groups could represent the Navy of the future. Park the big carriers and the USMC (along with their "aircraft carriers") will keep us safe. Their carriers even carry Marines and other stuff.
The cheerleaders and USMC have said as much.