I was in a
similar situation as you when I signed up here. I happen to install acoustical drop ceilings so I'm quite familiar with you data cable installers.
Regarding your question, yes, it is possible to make a truck more economical than a van, but it depends on which truck and van we are discussing. I'd say with 99% certainty that you don't
need a truck for your job.
Assuming you work solo and this is a work only vehicle, I would be looking at hatchbacks or the smaller station wagon type vehicles. With very little ingenuity, a 6 ft ladder and your stock (unless you keep a lot more on hand than they guys around here) will
safely fit inside a whole lot of vehicles, where my scaffold was a bit more of a challenge.
If you have a helper at times or you just can't see fitting your stock inside a car/suv, move up to a minivan search and just remove the rear seats. You'll be better off economically than any full size truck.