If you can't afford to just buy a real iPad mini, you're not really serious about developing and testing on the device.
You do realize that the iPad Mini won't ship until next Friday, and that people may want a head start on testing their app on a smaller screen.
And additionally, I'm sure there are a lot of small developers who can't afford to buy all the devices their software might eventually run on.
I've only just submitted my first version with in-app purchases to the store but if you get it now you will be grandfathered into some features when the update lands. http://itunes.com/apps/fastlists
I would have ordered the mini if it had more pixels (even at a higher price and lower battery life) but as it is I think I'll skip that version.