I would say a cab fare could be anywhere from $10-$15 depending on tip and your driver...
When we stayed at CBR we either:
1) Bus to MGM, boat to the Boardwalk, and depending on the time of night, either boat back to MGM or bus to DTD, then a bus to CBR
2) Bus to DTD, Bus to Boardwalk, Bus to DTD, bus to CBR