Well, how about US$2.99 for CoPilot Live Standard? It features a 2D map, with voiced turn-by-turn directions. CoPilot Live Premium adds 3D maps with lane assistance and alternate routes. It's $14.99 during the sale, which ends October 31.
In both versions, maps are stored onboard and don't need to be downloaded. The apps also include Bing local search, and weather information. The company also has extra an extra-charge traffic service which includes smart routing around congestion for $8.99 a year.
I've reviewed the CoPilot apps before and found them quite competent, but not as feature rich as some of the more expensive competition. I should note that the sale price in July for CoPilot Live Premium was $5.00 cheaper than the current offer, but both apps are still reasonably priced on sale.
If you're looking for inexpensive navigation that is iOS5 ready, then the CoPilot Live apps might be just what you're looking for.