Full service movers quote cheaper than U-Haul?

Trying to do a cross country move. Got a quote from a moving company that is $500 cheaper than renting a truck from U-Haul or Penske, or same price with full service. They said it's cause they're giving me the winter rate cause I'm booking it now but I'm still a bit skeptical. Is there some kind of bait and switch thing going on? Or are U-Haul/penske just jacking their prices up--they're quoting me $4800 for a 26' truck which seems really high.