Personnel for operating the rover couldn't possibly cost that much,.....I'm sure the communication infrastructure for it was already in place.
(1) Thos guys make between $85K and $120K per year. "overhead" about doubles that. This covers things like the building they work in, insurance, vacation pay and the bosses and office cleaning staff and capital equipment. So for $4M/year you get about 16 people full time.
(2) The communications system is HUGE. We are taling about football sized antennas all around the world, satalites in orbit and so on. All these cost money and every space program has to pay a "tax" based on usage and so on. So your $4M does not cover 16 people.
I've been in the software business for many years. I was surprized the first time I had to cost out a project. $1M does not buy many lines of code. We get about 250 lines of code per man-month.