I was actually thinking Super Hornet vs F-35B.
It seems cheaper to have a mix of SHs and Bs, versus an all-B or B/C mix. For example, how much weapons can the -B carry internally and externally versus the SH? IIRC, the max takeoff weight of the -B is lower than the SH, and an even lower bring back weight. I'm not sure about "endurance" as well (not sure if that's the right term) for CAS missions, i.e. how long can the -B loiter with an equivalent weapons payload as the SH?
You're talking apples and oranges here. F-35B won't be bringing anything back to a USN carrier and a Super Hornet won't be bringing anything back to an LHD and never the twain shall meet...
The F-35C that USN and USMC will operate will operate from carriers or land bases, so if the USMC were to acquire Super Hornet, it would most likely be at the expense of the -C model.
If the USMC weren't required to provide carrier aircraft, they wouldn't be buying either the -C or the Super Hornet, so if you want to save money, cancel that requirement and let the USN try to fill out it's carrier airwings...
It will be cheaper to buy 80-100 less fighters overall than the operate some ratio of mixed fleets. When operating from conventional runways under operational conditions that permit the carriage of external stores, the range / ordnance capability of the -B won't be significantly different to any other fighter in theatre, bringback won't be an issue (it's only an issue for STOVL operations).
Range? Well that depends on so many different factors it's hardly worth pondering. An un-refuelled F-35B's range conducting CTOL operations won't be hugely smaller than an un-refuelled Super Hornet, put it that way.
The F-35B will be bought by the USMC regardless of whatever else you want to equip Marine Airwings with, unless the aircraft or project is cancelled, so I don't see much in the way of savings to be had by running mixed fleets.