It depends how many devs take advantage of the new SDK which allows for universal apps. These apps will share the same codebase but when run on an iPad, will offer higher resolution, more features for the screen, etc over the iPhone version.
What sucks about this, for iPhone users, is that many of their apps will grow in size because of this. It will be interesting to see how this plays out, especially since many devs will want to make money off the iPad only version, and many iPad owners will have iPhones, etc and get it for free in this manner. However, some devs might bet that people will be more likely to purchase their product if it supports both, and might see the benefit in overcoming the competition. Again, we'll see.
As for the price of iPad-only non-universal versions, I bet they will top out around $15 for the AAA titles. Plus there won't be as much competition at first. The most money I spent on iPhone apps was probably the first few months when everything cost $10. That was painful, especially looking at what you can get now for $10. 10 apps!
I also don't see many iPad apps being sold for below $5, aside from some basic games or other really simple apps that have limited functionality to begin with. Like fart apps. But for some reason I don't see the iPad as being a big market for those types of apps anyway, and hopefully we will see less of them in the iPad section. Seems like more productivity and AAA game titles to start with, which is absolutely fine by me. Apple released their Texas Holdem game for $4.99 when the App Store debuted, some say, to set a lower pricing scale by example. I think they did the same thing with iPad, but with grown up, feature rich apps at a decent, although higher standard price point then the earlier game release. Apple, if you're reading, PORT APERTURE! Oh and iPhone syncing / tethering. Thank you.