I made my living selling telecom hardware and services for 25 years, so I know how to sell and when someone knows their stuff.  I bought a tow dolly from a trailer/RV place.  Salesman was the son of the owner, basically grew up on the lot.  Tow dolly had "Dexter" axles and he made a big production of that, said the "Dexter" rubber torsion spring axles were the best.  Arguably true, but this tow dolly had a plain dropped axle, not a torsion spring axle, and we were standing there looking at it.  I pointed this out, got attitude back so I asked if having the "torsion spring axle" made it more expensive than a plain dropped axle, he said "nope, that's the way they come".  So I bought it and got out of there before I lost it.  He set the tire pressures "right" for me, as soon as I got off the lot and around the corner I dropped them from 50 psi down to 30 psi, which is what the big label on the tongue said they should be at...
Brian