Although not a good look, it is ok for the treasury to go broke. The critical parts are the validators and the fellowship, neither of which rely on the treasury. Kusama is a canary net, not a business. ROI is what is learned, reputations built, and all the extra-chain coordination that evolves.
The big treasury to start is like baby fat for a growth spurt at the launch of OpenGov to initialize the coordination of human actors around the chain. As we go along and learn how to operate the machine better we will trim away the dead growth and lean up as treasury inflow/outflow comes into balance.
What is the Kusama treasury for?
"The Kusama relay chain exists as a security hub for parachains and for testing / Scaling of Polkadot’s core mechanics:
- Parachains Protocol
- Consensus and Finalization
- Staking
- Governance
- Parachain Scheduling
- etc…" -Paraphrased from a comment by Shawn Tabrizi here: A Kusama Forum - Place for longform debate and healthy discussion - #14 by shawntabrizi