I notice that the price at a localbitcoin sit is much higher than online price. Is it more expensive to buy bitcoin from localbitcoin sit than to buy bitcoin with credit card?
Yes because when you're buying from Localbitcoin you're buying from people looking to make a profit. When you're buying from a website and using your card the merchant has to pay fees for using visa/mastercard network (like any merchant online and offline as well) so the website forwards the fees on the buyer.