We went through the WARDOGS item catalog: it contains 474 items in total, and 344 of them have a listed price. This analysis produced an unexpected result.
A backpack more expensive than a tank
The Halftrack Backpack — the biggest backpack in the game, thirty slots, weighing 2.78 kg — costs $15,000.
By comparison, the L2A6 tank — three crew slots, a cannon, a coaxial machine gun, and an M249 — costs $14,000.
In other words, cargo space costs more than the combat vehicle meant to carry it.
Catalog price range
The cheapest item in the catalog is a .45 ACP round at $10.
The most expensive is the Havoc helicopter at $18,000.
A full set of level 4 armor costs $7,000.
See the full catalog with prices, weight, and grid size on the WARDOGS catalog page.