Network fees are the fees that are paid to directly to the blockchain’s validators to process transactions. Ultimate does not collect network fees, they are necessary in order to use the blockchain, no matter which app you transact from. We chose to build on Solana because fees are extremely low, (currently less than 1/10th of $0.01).
Network fees are paid in the native token of that blockchain, so you need to keep some non-zero amount of SOL tokens in your wallet in order to make transactions, even when transacting tokens that are not SOL tokens.