Bundlers collect "bundles" of Nocturne operations and submit them on-chain. Users subsidize bundler gas costs with additional tokens unwrapped in their operations.
Nocturne utilizes batch verification of Groth16 proofs for all operations inside a bundle. This means that the more operations in a bundle, the lower the verification cost per operation. Bundlers can decide on the bundle size and contents by weighing a bundle's transaction cost against and the user gas fees included in the bundle's operations.