Your cost for bare shafts is pretty close to what I see around here. Pulling that weight at 70 years old is impressive and I don't blame you for trying to hang onto your youth.
I have no desire to pull a bow that heavy. If you want to continue shooting that and the cost is prohibitive, do you need 30 shafts? Would 10 work? 5?
Just a thought. Add some extra walking into your "workout" by retrieving your arrows more often.
-Jake