resale value vs. loan balance

06 Cobalt SS S/C
60 month 4.75%
bought for 25700
Traded in my brothers wrecked 1983 Olds for 300 bucks.
Sold my brother my cavalier for the difference of the monthly payments if i traded it in. He pays me the difference monthyl for the next 5 years.
I owe around 18k on the loan
KBB private party of 19205-excellent 18100-good

if memory serves me right those values are actually up some from 6 months ago.