What a fee actually pays for
On a monolithic chain, every transaction in the world is a bid for the same commodity: inclusion in the next block. Blocks are bounded, demand is not, so a market forms. The fee is not the cost of computation; it is the clearing price of contention.
That is why fees spike when something unrelated to you becomes popular. Your transfer is competing with a mint, an arbitrage bot and a liquidation for the same finite space.
Removing the shared resource
Rubix divides the global state machine into a large, finite number of token chains. Each token carries its own chain, its own state and its own history. A transfer touches only the chains of the tokens involved.
Two transfers between unrelated parties therefore have no resource in common. Neither one can delay the other, and neither has any reason to outbid the other. There is no queue to jump because there is no queue.
You cannot auction a resource that is not scarce, and you cannot make blockspace scarce if there is no shared block.
What replaces it
Validation still costs something, and that cost is met by the pledge mechanism rather than by a per-transaction fee levied on the sender. The result is a network where a transfer's cost does not vary with unrelated global demand.
Where the model is harder
Independent chains make contention rare but they do not make it impossible: two transfers that genuinely touch the same token must still order themselves. The protocol resolves that with the same quorum machinery it uses everywhere else, which is a narrower problem than ordering all activity globally.