I'm not sure if it's cheaper worldwide, and paying in 6 month chunks isn't for everyone, but it's significantly cheaper for me in the UK to buy gamecodes from the Origin store rather than pay directly through the site.
Never had any trouble this way, had a few issues with the account site though. Well, I lie. My bank did lock my account because I made like 20 identical purchases from the Origin store once when I was buying Soulstones. EA really need to let you buy multiples of the same item.