The firm's payout obligation is real; the trading is not. Orders are matched internally against a price feed, so the firm's profit is the difference between subscription and evaluation fees and the payouts it owes. It bears no market risk from your trades because there are none.
This creates incentives worth understanding. Rule enforcement, consistency-rules and drawdown thresholds are the firm's risk controls on its own payout liability, not on market exposure. Fills may also be better than reality, which flatters strategies that would suffer real slippage.
Example: a scalper takes 300 trades a month at 1 tick of edge on a contract with a $12.50 tick. In simulation, resting limits fill whenever price touches them: 300 fills, $3,750. Live, roughly 40% of touched limits do not fill because of queue-position, and the same strategy nets closer to $1,100.
Related: live-funded-account, funded-account, payout-split, evaluation