I haven't seen an annual figure average for a PPL, but in both RA and GA cost is the limiting factor.
For PPL, hire rates at Royal Victorian Aero Club are currently (per hour):
C152 $245.00
C172N $280.00
C172SP $290.00
PA28 Warrior $285.00
PA28 Archer $295.00
PA28 Arrow $345.00
One of the best plans I've seen for staying current at the bare minimum annual cost, was a guy who did 30 minutes per week. He didn't fly on bad weather days and he took holidays.
So on current costs for a C152 that would be:
40 weeks x 0.5 hrs = 20 hrs/yr x $245.00 = $4,900.00/year
That was in one of the busiest circuits in the country, so he was always on his toes and up with his pre-flight, pre-takeoff, circuits, downwind checks, landings etc.
RA rates for RPC
Jabiru J170 $110.00, $174.00, $220.00
Jabiru J230 $207.00