Why do Marines needs to buy C models? The Marine Corps doesn't get much out of a Squadron that is part of a CAG in our MAGTF. Some old guys around here have enlightened us that the Marine Corps presence on carriers is pretty much because the Navy wants more squadrons but doesn't want to pay for them. The Corps buying C models will create huge costs in training, maintenance, parts etc.... You would essentially be creating a whole new airplane. No other service is going to operate two versions of the airplane. Why should we?
Holy hyperbole Batman!
Whoa there yut-yut, I not sure you quite realize just how closely tied the Navy is to Marine aviation, especially when it comes to funding. As it has been discussed here before aviation funding for the Navy and Marine Corps basically comes from the same pot, so essentially the Navy as well as the Marines is paying for those VFMA squadrons on the carriers. To claim that the Marines buying C models will create huge costs in training, maintenance and parts is also a bit of a fallacy since the Navy and Marines are joined at the hip when it comes to all of that good stuff. More importantly the different versions of the F-35 have also been designed and built to have a great deal of commonality when it comes to parts, training and maintenance so there wouldn't be 'huge costs' buying some C's vs B's, and it is nowhere near "creating a whole new airplane".
In the grand scheme of things the VSTOL F-35B almost certainly lengthened the development as well as increased the cost of the overall F-35 program, making the basic design of the aircraft be able to perform the VSTOL mission was challenging for both teams that competed for the JSF. Basically everyone else is helping pay so that the Marines can have their VSTOL F-35B. You can thank the USAF later.
In the end the possible mix of F-35B vs C's in that the Marines might fly will be done at a much higher pay grade than anyone here on this board and who knows what they will decide.