CoPilot USA is a great inexpensive alternative. It's $4.99 and an additional $2.99 for text to speech if you want that. I used it for awhile but when Navigon dropped to $25 I got it so that's what I use now but CoPilot is great for your budget.
I would agree that MotionX is pretty darn good for the price. Whats really useful is you can simulate your trip so the maps etc are downloaded before the trip.