One can trade Vanguard's ETF with no fee for buying or selling. I have made several trades ( on the internet - no agent) over the last year for no fee. How do they make money ?
Vanguard is in an ETF price war with other brokers and they are all under pressure from brokers like Robinhood which offer free trading and are growing rapidly.
Vanguard is more of an asset manager and its profits from trading is far smaller than online brokers whose lion's share of profits come from trading commissions. By eliminating commissions on many ETFs, Vanguard is foregoing some commission revenue in exchange for stickier assets. “Sticky Money” is slang for investors that will stay around for the long-term.
Vanguard also offers traditional brokerage services, variable and fixed annuities, educational account services, financial planning, asset management, and trust services. Think of their 'no fee' ETF service as a loss leader aimed at attracting new clients and then offering them other services where they can make more money.