caveat: the following comes from one at the other end of the spectrum, with three paid in full vehicles.
How much is still owed on the vehicle and what is book value that you could expect to receive if you sold?
Personally, I don't see the issue with the $450 unless you got it down to that by stretching the loan out to one of the insane five year (60 month) or longer terms where you are upside down from the get-go.
If it makes sense to sell and get a beater, your insurance will likely drop as you could then get away from the requirements for collision (I still keep comp even when I drop collision though)...and for the younger drivers, collision seems to be a big chunk of the insurance bill. Other issues will involve how registration fees are determined...some States really gouge owners while others (ie. Texas) get somewhere between $50-80 for most vehicles. It makes no sense to pay large registration fees on a vehicle that won't be driven...