That's all available on phones and far more as well. To each his own but paying $600 for a single function quick to be outdated device is not my cuppa.
Manufacturers have apps for their particular brand and they can all build routes import the GPS files and far more.
http://www8.garmin.com/apps/
I suspect it's habit rather than effectiveness.
Couple of years ago I might have agreed with you ....not now.
This is a good overview and
http://www.advpulse.com/adv-prepping/have-smartphones-made-the-handheld-gps-obsolete/
and when cost is taken into account plus future proofing...no contest
I think you need to explore a bit more.
I've spent time travelling with a stand alone GPS rider and they seem to spend an inordinate amount of time peering at the screen.
The iPhone offers unparalled flexibility when riding by having access to a variety of solutions from traditional offline GPS like TomTom to a whole range of apps incouding those like MotionGOS that can import GPS files.
I can listen to iTunes and the GPS lady whispers in my ear where to turn and then puts the music back on.
GoogleMaps to GPS files is a useful trick for iPhone or Standalone GPS users.
Creating GPS Routes from Google Maps
http://triduffer.wordpress.com/2013/12/15/creating-routes-from-google-maps/
The biggest advantage aside from cost is the smartphones move forward all the time.
Many like me want tunes, phone communication, email and nav including voice nav all on the handlebar plus the ability to access apps like TripAdvisor, Urban Spoon and others that make travelling so much easier.
Being able to switch to the latest and greatest Nav app for maybe $10 at most is terrific.
I love
TomTom for ease of use and its Winding Roads feature but then I want to switch to more flexible online apps when in cell range.
Offline there are pros and cons.....add in online access and it's no contest.
And the phones keep getting brighter and the variety, ease of use and sophistication of apps moves forward month by month.
It's a competitive nut house out there.
I'm not sure the stand alones are winning the evolutionary battle.
Besides...the OP wants a cost effective solution t'would appear.