Its "the publishers, who decide to set their games at prices up to two
or three times the cost of the iPhone version.
But the worst part? Not only is the content of overlapping titles
generally no better than the iPhone; sometimes it's worse.
You see, PSP Minis can't have any network or online features. Nor can
they support camera peripherals (a major focus of DSiWare innovation)
or DLC. Kotaku just reviewed iPhone port Hero of Sparta. On the PSP it
costs triple what you'll pay at the App Store. Their review?
"Simplistic controls, muddled graphics, and abysmal sounds turn what
was a fantastic iPhone game into a oddly disjointed PlayStation
Portable experience." Kotaku's review of Tetris was much better. But
you know what? Tetris costs twice as much on the PSP as it does the
iPhone.
Some will say, "Well, you get what you pay for." But that's entirely
our point. If you glance across the two platforms, you aren't getting
what you're paying for. You're either getting less, or you're getting
a lousy port or, best case scenario, you're getting basically the same
thing for more. "
http://news.cnet.com/8301-17938_105-10365818-1.html 
INTERESTING:Gizmodo on iPhone vs costly Sony PSP for games 
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