Bowling balls at 400fps...
I shot a 1200 gram steel/ice projectile from my burst disk gun @385fps, and the recoil was sufficient to rip a stand made from 4x4s to shreds.
For the kind of power you're looking at (roughly 25 000ft/lbs), you will likely need to include wheels so that the whole thing can roll back on firing, or at least shock absorbers with rather long travel. A fixed stand would only destroy itself over time.
As far as cost goes: most parts will need to be obtained on the cheap. A 4" union (the largest size available) will set you back at least $150 new.
If you want porting larger than 4", you'll either have to use a flange, or make your own disk holder.
Does anyone know the diameter of a bowling ball? Because EVBEC says that with a 10' x 6" barrel, he could easily get 10 pounds over 400 fps with a 4x mix.
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.