If you're doing those things at arms length, it's really difficult to keep those costs down. Your only option is basically an internationally known Tier 1 law firm. They are _not cheap_. Not only will they bill you plenty per hour, they will take a heck of a lot of time making absolutely certain before they provide an opinion as they don't want to expose themselves to liability.
Whether or not it justifies every price hike out there is in the wind. There are still non-trivial costs associated with doing business in another market even in the digital age, though.
Source: have done digital business in many, many countries from Australia as a base. Have had legal docs localised into AU, US and UK law. Paid staggering amounts of money to lawyers for same.
In any case, there are zero tariffs on digital goods between the US (where most games are made) and Australia, due to the free trade agreement. [1]
So, you have an environment where there is less tax on the goods than in the UK, yet the prices are higher. The answer is not "government has its finger in the pie". In fact, the GST at 10% isn't that far off sales tax across the US, which is generally 7-9%, so seriously, the answer really, really isn't "taxes".
[1]http://en.wikipedia.org/wiki/Australia%E2%80%93United_States...
Imagine a law that says, "The price of Photoshop in Australia cannot be more than the price in the US". Wouldn't that law be economically similar to one which says, "The price of Photoshop in Australia cannot be more than $400"?