An L2S (Supersprints, hillclimbs etc) licence is $66 from memory. That’s for a year, but to participate you also need to be a member of a CAMS Car Club - TDRC, LCCT, HSCC, NWCC etc. TDRC membership is $40 I think.
For the state and national circuit races and series you need what’s called a National Circuit licence, I just got my renewal (and lost the paperwork already!) for this and it is about $400 + medical ($100) + Car club membership.