There will be a lot of cardboard generated by your vendors, and you should look to capture as much of it as possible. Although it would be nice to compost this material, that's just not feasible now. At best, this material is trash. At worst, it will contaminate recyclables if not disposed of properly. Sometimes there are local markets for a material, and sometimes those markets disappear overnight.
Prices fluctuate too, sometimes monthly, sometimes daily.
Markets also vary by hauler. Different haulers handle different materials. Some haulers prefer to handle only materials on a long-term contract basis, and others handle materials on a spot market basis. These differences will affect price as well as the availability of markets. Talk to several recyclers and haulers to see who best fits your needs, and to find out about current market conditions.