question Expert Advise needed - Why are "ForSale.com" domains sell for higher price?

Hi Team

Going though namebio site identified that "forsale.com" domains sell at premium prices

Appreciate your comments as to why "ForSale.com" domains sell for higher price?

Some reference from namebio
boatsforsale.com
worldforsale.com
robotsforsale.com

what domains should we buy, what should we stay away from?

Thanks