Hi Dmitri! Don't believe what Apple tells you about making money in the App Store. It's not as easy as it sounds. ;) I myself registered for the paid iPhone developer program last year and was not able to publish any single app. It's not enough to have a killer app idea, execution is the key. You're app must be able to stand out above the multitude of apps already deployed in the app store.
My suggestion is don't register for the paid program unless you are almost ready to deploy. Yes, it's hard to test using simulator only (not all functionality is supported) but you can register anytime you feel like you're ready.
But if you love programming and would love to join the iPhone dev to fuel your passion, then go ahead and fire away!
Initial costs:
MacBook or Mac Mini which runs Snow Leopard
Your time
iOS SDK (free from Apple site)
Optional costs:
iPhone Dev program enrollment (for deploying to device and publishing to store)
iPod Touch/iPhone/iPad for testing