When you say "truck camper", I assume you mean a pick-up with a camper on back.
I have seen pick-up campers stay at both camp sites and parking lots. I was at an ACE campground last week and two truck campers spend the night in one camp site. I assume that they only paid for one site. I paid $20 for my RV, they could have split the cost and only paid $10 each for the night.
On the other hand, I have seen truck campers spend the night at truck stops and rest areas or Wal-Mart's or Flying J/Pilot stations, etc.
With a smaller camper, you may even find friendly folks that would let you stay in their drive way or in a field by the house, etc.
Have fun and have a lot of good time camping.