These options should come out to average $50/round. I have missed a few that are actually in Charlotte, but this should give you an idea.
Golf Club at Ballantyne is a resort course that will run on the pricer side of things but is a reasonably fun course. Fort Mill, SC is just 30 min from Charlotte and has 3 good courses to play. Further south is Rock Hill, SC. Just off of the interstate is Waterford Golf Club--just bought by the owner of the Panthers, it once was a good course and should be again soon. West of Charlotte is a course called Crowders Mountain ironically in Kings Mountain, NC. I haven't played there in a few years, but it is a tight course, not overly difficult but definitely was worth more than the greens fee at that time.
My personal favorite is a course that will certainly stretch your 90 minute radius but it is worth every minute of driving. It is a well kept secret and a hidden gem. Edgewater in Lancaster, SC--if you can make the trek GO THERE.
Charles Sifford is a muni just outside of uptown Charlotte, and is not a destination by any means, but it is a good extra toss in round. I played it last around October and it was surprisingly well kept for the traffic it receives being a muni in the city limits. Again, it is a good toss in for close by bonus round, don't plan your trip around it.
What time of year are you traveling?