No, there used to be a point in time when you could buy anything. Zombies weren't buffed to hell back then so people with good movement skills would just buy boomsticks, load 2 shells in, and 1 shot any zombie up til wave 5 when it'd increase to 3-4. Fast zombies gave up as they were getting 1 shot without doing any damage. If it got to be too many, the boomstickers would rocket back to a shitcade where you load 4 shells in and 2 shot bosses.
Those were dark times for zombies. We all made a profit too.