You can already do this at Coinbase but yes, I would pay a small fee to transfer instantly. I think this is what a lot of people use sites like Localbitcoins etc for.
You absolutely can not do this instantly at Coinbase, as it's not an exchange. Read the thread again. He's not asking if you'd pay a fee to buy coins instantly. He's talking about utilizing two exchanges for arbitrage (ie. sending from Bitstamp to Kraken instantly).