What makes some cell phones worth ten times others?

I like my $39.00 Android phone and it does everything I need it to do.
It runs out of memory if you put to many apps on it (some won't transfer to the external card) and it doesn't have call by WiFi if there is no service. There may be other things but kids tell me they only spend $45.00 a month for the phone and that just gets added to there monthly bill. No phone can be worth that much.