Nifty Arena aims for a sustainable business model that is not reliant on continuously selling NFTs. The business model aligns with the core idea to build a savings account you can play with.
Phase 0 of the game is all about Community Building and will not have a business model
Phase 1 of the game will offer NFTs that can be minted with DAI or ETH, using yearn vaults to capture the interest of the deposited funds.

Screenshot of the concept deck, found here: ‣
Rally.io has built a wrapper for Yearn Vaults that sends the accrued interest to a 3rd party wallet, called Yield Delegation.
The interest will then be sent to the game treasury that is used for development expenses and game rewards. Here's a simple napkin math of what to expect:
Monthly Active Users: 10,000
Avg. Deposit / User: $ 5,000
Annual Interest: 10%
Annual Revenue for the treasury: 10,000 * 5,000 * 0.1 = $5M / year
Note: Details of the business model are TBD and will evolve as the game and community takes shape.