The amount of money someone puts into a vehicle is of their own discretion. I could buy an entire quad for the amount of money I've got into my front axle. That being said, you could buy an entire truck for the price some people have into the quad suspensions/etc.
I can haul a quad in the bed of my ranger. I cannot haul a truck in the bed of my ranger. Wheeling a truck requires an adequate tow rig, trailer, license/maintenance/insurance for each as well. If you drive your rig on the road, you've still gotta pay license and insurance, and maintenance skyrockets as it has to be able to safely travel at those speeds without worrying about catastrophic failure.
Quads are smaller, easier to store, easier to load, cheaper to maintain, already built for offroading, and all around easier to own. If you wanna go wheelin, you toss it in the bed of your truck and go. If you wanna wheel your truck, you hook the tow rig to the trailer, make sure all your tires are up to pressure, make sure the trailer still operates properly, trailer brakes still work, trailer lights still work, load the rig on the trailer, strap it all down, blah blah blah.
Trucks are a pain in the ass lol.