The Bancor Vortex charges a protocol-wide administration fee paid by liquidity providers. The fee is taken directly from swap revenue, and is adjustable by the DAO. Fees are swapped for vBNT via the vBNT/BNT liquidity pool and burned, creating deflationary pressure on the circulating supply of BNT.
You can learn more about it in this video explainer, and also by reading this guide.
