Not Robinhood on the other end of the transaction, but yes. If you and someone else both mashed SELL at the exact same instant, they'd get $48 for their stock

Not Robinhood on the other end of the transaction, but yes. If you and someone else both mashed SELL at the exact same instant, they'd get $48 for their stock and you'd get $47.99 and your confirmation screens would both say "we sold your stock at the highest price we could find". In exchange for sending their customers to a place where they'd only get $47.99 instead of $48, Robinhood received direct cash payments.