The thing you are missing is few NBTA members pay ANY mooring fees, as far as I can see!
But I understand the point you meant to make. I just posted in an over-simplifed manner to make my own point that both mortgage-holders and renters living on the bank have seen far larger increases in their expenses than CCers and CMers.
Boaters without a home mooring, even after the rises are applied, will still be enjoying the cheapest accommodation available in England and Wales by a long chalk so deserve little sympathy.