you already said without shipping. There's the shipping cost to factor in too.
Even if it's really cheaper, you will have to go through the trouble of the online ordering procedures. Not to mention having a certian level of risks when dealing with online shopping. Risks such as flactuation of currency exchange, reliability of sales person and middleman(if there is) etc.
Getting the cards local, on the other hand totally remove the risks associated with online shopping. (you can physically see/feel the goods, and also check for damages or broken seals)
well, there are much more things you have to consider before purchasing the cards via online.