The singular is straight forward, direct meaning and far superior than the plural, even in the Dot Org. Who buys more than one car at a time, anyway? The singular passes radio test, IMO, and holds more value than the plural. The plural sounds silly and leaves room for error.
The Org Extension does hurt it a bit, but not much. Com will always be king, but in this day and age, typically not as many buyers care as much as they used to with regard to extension, as long as it's among the three main, Com, Net, Org.
IMO:
Low $xxx to low $xxxx, end-user.
$xx to low $xxx, reseller.
Again, IMO!
Good luck.