I got the $30 sale version at Harbor Freight, replaced the bolts and nuts wih Home Despot nut's, bolts, LOCKWASHERS, and loctite'd them I use it for hauling Target stands and the like big. bulky and relatively light things that I don't want to tear down to fit in the back of the truck. I also tie the top of the load down to points on the truck bed to prevent twisting and bouncing.
Will it or similar ones carry 500 lbs? probably. (Although if I was to put 500 in ona regular basis I would weld some additiona gussets on and reinforce the connections at the tube. That looks like you could easily torque it and twist it off) Could most trucks handle a 500 lb tongue load? No problems. Could it really mess up your handling? OOOHHH YEAAAH
The rear end on my truck is prone to break loose on some turns anyway when empty, I'm sure a 500 pound load back there would really tend to pull it out on turns.
If you have really loaded up your truck to the point you need more carrying capacity, you better check on your gross vehicle weight. BTW I broke a leaf on one of my 3/4 ton truck springs when I got close to the gvwr, the GM/Chevy design in 88-90 had spacers in the wrong places. I went over a rr crossing and the bouncing did it.