They chose paypal.
So, the inconvenience (and expense - might have cost them $7 in exchange fees) of acquiring the bitcoin was not worth $40 to this buyer. A tech-savvy buyer, based in San Francisco.
It's anecdotal, but I think THIS is exactly what bitcoin needs to overcome to hit mainstream use. It's got to be easier for consumers to acquire/pay using bitcoin. The incentive has to outweigh the perceived hassle.
Indeed.
I suppose he would pay for the coins at the exchange with Paypal or with his credit card, so one should add the fees for that to the $7. And then there may be a delay before the money is available for trading. And another delay for moving the coins from the exchange to BitPay or to you.
Volatility is another big obstacle.
If you post the bitcoin price as a fixed amount of BTC, you run the risk of the USD/BTC rate going down, in which case you would lose money. (Last Friday it dropped 8% in a couple of hours, for example.) A smart customer or competitor may wait for the rate to drop, and then buy lots of merchandise from you at below-market price.
Conversely, the customer runs the risk of the rate going up while he is buying the bitcoins. To guard aganst that possibility, he has to send perhaps 5-10% more money to the exchange than he would need at the current rate. If the rate does go up that much, he will end up paying more via bitcoin than via Paypal. If the rate does not go ub by that much, or goes down, he will be left with a few extra dollars at the exchange, or a few extra BTC; which he must retrieve and spend elsewhere, otherwise he would lose money all the same.
If you post the bitcoin price as "the BTC equivalent of 360$", you merely push some(but not all) of your risk to the client.
I gather that Coinbase and Paypal have some mechanisms to alleviate some of these risks and hassles. I don't know the details, but even if they offer a fixed USD/BTC rate for the day, it only reduces the volatility risks, it does not eliminate it.
At this point, bitcoin payments options are advantageous only for people who already own a pile of BTC and want to cash on some of it to buy stuff. Those options let them skip a couple of steps in that process.