3G model is a joke, don't even consider that.
In USA its $15 a month for 250MB of data (A stupid amount for a PSV) or $30 a month for 3GB, unlikely you'll use that much data unless you constantly use 3G, but $30 a month is steep for something like a PSV and I can't see how it costs Sony £50 more to make a 3G model, insane.
And yes, like the MS Pro Duo, the memory cards are annoyingly expensive. They should have gone down the Nintendo route and used SD cards, they're common, cheap and have decent read/write speeds.
Sony's reasoning for using their PSV Memory cards, was 'We want to ensure that the cards provide optimal performance', basically. Which is funny, because the MS Pro Duo was a disgrace when it came to read/write capability.