Why did my base upkeep get more expensive?

On PvP servers the cost of keeping your base standing is no longer a flat rate. It depends on two things.

The size of the building. The more structural pieces it has — foundations, floors, walls, doorways, windows, roofs, stairs — the higher the surcharge on top of the base cost. It rises in steps, and the largest builds pay up to double. Doors and hatches don't count: they still cost upkeep, but they don't push you into a higher bracket.

The number of authorized players. Up to four authorized players cost nothing extra. Above that, each one adds a surcharge, counted from the total — so a cupboard with seven people costs noticeably more than one with four.

On PvE servers none of this applies — the upkeep there is the base cost only.

Discounts still work on top: if you have PREMIUM PLUS or a clan upkeep perk, it applies to the final amount.

What to do about it. Open the cupboard and look at the daily cost — it always shows what you're actually paying now. If it's higher than you'd like, the two levers are the same two things: build more compactly, and keep the authorized list to the people who really need it.