Dirt cheap: I rode tons of miles on unknown roads using paper cue sheets. Cheap, glitch free. Requires pre-planning with a PC. Waterproofness takes work. Not flexible in case of closed roads etc. Navigating at night is slower. Navigating at night in the rain is even slower. But it's cheap. With a phone as backup in case of detours, it's a decent way to go. Just make sure the phone stays charged and you have offline maps.
$100: I have a Lezyne Macro GPS that works okay. Requires a cell phone with data connection in order to start riding a route. For creating routes, a PC is needed unless the recommended routes are okay. You can re-route on the fly, again if you have a phone with data, and as long as you're okay with their recommended routes.
$150-$300: Garmin eTrex 20x is my current nav device. Rechargable AA batteries, but the ability to buy throw-aways virtually anywhere, if I misjudge. Downside is it's not wireless, PC is required, visibility in direct sun isn't great, UI is "expert friendly". I think the newest model is $300, used 20x models for around $150.
A note on maps and cue sheets. I think that counties and cities in the US are less diligent on maintaining road signs than previously. I suppose since more and more people are using navigation in their car, basically following the blue line, signs aren't needed as much. Cost savings.
Cheers