Oh! I think I've got it now! Seriously, I had to go glare at a wall for ten minutes until my brain suddenly put it into RL terms and it makes sense. LOL. It's so late at night right now.
Okay, so in RL terms, if you buy land or a house, you pay the purchase price up front to the seller, but you still pay the council rates every month/quarter/year. I'm not sure what it's called in other countries, but here you pay a fee based off the amount of land you own, which covers services like garbage collection, drains, etc.
So in RL terms, tier is the council rates, yes? So my premium membership covers my "rates" for owning up to 1024sqm, and anything over that I pay extra rates for?
Okay so if I buy a mainland parcel that's less than 1024sqm, I just pay the purchase price but no ongoing fee?
Sorry for the confusion, all! I've barely even had to rent a parcel on an estate for the last decade. I mostly just slum it on a friend's land. LOL.