"Work trucks" is a very broad phrase encompassing any sort of truck or truck-like vehicle used for the purpose of working. If you Google such products, you are sure to get quite the variety of responses, and lots of trucks that vary immensely with the tasks for which they may be used. The following is just a few examples of the many different trucks that are used for work purposes, and where you might find each.
Lightweight and Heavy Duty Pickups
While just about anybody can find and buy these trucks, you might buy a lightweight truck to haul tools, or you might buy the heavy-duty truck (the kind with four wheels in back and two up front) to haul a lot of heavy supplies from a store/supplier to the job site.
Both types of trucks run the usual MSRP at any car and truck dealership where passenger vehicles are sold, and you can certainly use them for transportation outside of work as well. A lot of companies needing standard trucks for hauling resort to this option because it is the least expensive one.
Utility trucks are like the pickups in body styling with one major difference. They have utility cabinets welded onto the sides of the beds of the trucks.
More commonly used for repair trucks and electrical or utility trucks, you could use these vehicles for a number of other work-related applications really. Utility trucks can only be purchased through dealerships that specialize in small work vehicles.
Other Small Work Vehicles
Other trucks that still look like pickups with additions include cherry picker trucks, crash trucks, roadwork crash prevention trucks, and tow trucks. All of these may be available through the same dealerships that sell utility trucks, or you may find them through other specialty dealerships. You can expect the price for each to be on par with a heavy duty pickup truck plus the cost of the extra features on each vehicle.
Construction trucks are definitely the largest, most expensive work trucks you can buy. In this category of trucks, you have dump trucks of various sizes and any other construction vehicle that is road-safe (i.e., you can drive it on the road from one place to the next without causing traffic jams). Construction trucks are only sold through construction truck manufacturing companies and their pre-approved dealerships. For more information about buying work trucks, contact a dealership near you.