I've been keeping my price limit low... I only bought pricier items when they went on sale. That being said, I did buy Mote-M, Band, and would have bought that $5 note app that I can't remember what it's called, but I didn't have enough credit. Mote-M was a disappointment, especially when it went on sale for a dollar right after I bought it. But Band was well worth it, and if I had bought it I'm sure the note one would have been too.
My dad bought and sent over to me xplane, asphalt, and galcon for bigger ticket items. I would have bought all three instantly myself, and know that they're worth the money. They're the best ever.
I just got billy frontier on sale for a dollar as opposed to $5. I wasn't about to pay for it at $5 and still wouldn't, but it makes a nice dollar game.
Most of my apps, as in 75%, are free/demos and I enjoy those too. It's amazing how much great free content there is. I also have a bunch of great $1 purchases. Oh yeah... I also got Apple's Texas Holdem, which is amazing as a poker app and graphics wise. I paid $5 for that and am happy. If you actually read all that, I hope it helps!