The last stand alone GPS unit I purchased cost me around $15. It has a very sensitive SiRF III GPS receiver and a very long battery life.

http://www.amazon.co.uk/Navicore-Three-Bluetooth-Including-Charger/dp/B004ZDOR9S

It can be used with a huge array of electronic display/map systems that have a Bluetooth connection. It works with a ruggedised cellular phone (which also has a GPS built into the handset as well so has some redundancy)

Current Cellular handsets have a much higher screen resolution for displaying electronic maps but are not very rugged when compared to standalone GPS electronic mapping display systems of a similar handset size.

I still use a paper map and a compass though as the GPS signal isn't always guaranteed to be available and electronics can fail and batteries die.

A stand alone GPS is useful though if you don't want your handset manufacturer, service provider, government google authorities not knowing where you are.