We are not talking 4 million, the budget is 22 million.
You also forget the R&D phase is over. We are in the operational phase. 4 years plus.
As to the grad students, nothing polishes a resume like a stint in a NASA control room.
Give them $15/hr, 40 hrs a week and let the rovers have weekends off. That way both planets can start off Mondays with recharged batteries.