VIP5+ plan. A split order costs a VIP5 or VIP9 desk about its fee, 2.3 to 3.1 bps, so OneBook cannot win them on a fee. The plan has no taker fee, and the house maker quotes at its cost floor plus 0.25 bps. The floor is adverse selection (0.4 to 0.8 bps), stale quotes over 2 s of exposure, hedging the netted 12% of flow passively at 1.5 bps plus its impact, and bond carry of 0.05 bps.
The plan holds only if the hedge is passive, netting stays near the median, and the maker widens or pauses when volatility spikes. Revenue at 0.25 bps is $10,000 per $400M filled a month.
Market impact. Splitting does not avoid impact. A worked order still moves the price by about Y · σdaily · √(order / daily volume), the square-root law measured on Bitcoin by Donier and Bonart (2015), with Y = 0.5 to 1 (BTC $1.11B/day, σ 1.82%, ETH $0.55B/day, σ 2.57%, SOL $0.18B/day, σ 2.32%). OneBook pays impact only on the flow its maker hedges: 12% of gross flow in a median 30-minute window, 50% at the 99th percentile.