I'm sure you could get a new live action series for under 3 million, the biggest factor is your payroll (specifically the cast) and what CGI house is used (though CBS has their own). Sets are another big consideration, how much physical vs virtual. Also I would only do 13 episode seasons (13 x 3 mil = 39 mill), unless the show is a hit and warrants more episodes.
Star Trek does not really belong being broadcast on CBS given there current model, however, consider that CBS is winding down there CSI an NCIS franchises so they may have room to try some different things.
Lastly, also consider that Star Trek is popular internationaly, so CBS can offset a lot of costs by licensing 'second run' options to various foreign networks, these tactics have helped BSG and Doctor Who. Germany alone has a huge fan base. Star Trek has a huge advantage here vs. any other show, CBS would be smart to work on that angle to offset costs.
A Star Trek series can work, the next movie will be a test of continued popularity. Reminds a little of how the success of Star Trek 4 helped get TNG going.