I have done 300 but have a 24″ flat top and 2 full size steam tables to keep everything warm. 400 dogs and your existing set up is alot! I concur with some of the advice so far:
1) forget steaming buns
2) separate table for condiments
3) larger facility to prep the hot dogs
4) use your steam table to hold
5) one person tending to the cooking
6) one person handing out the cooked dogs
I would not pre-wrap if possible as the visual of slinging the dog from the steam table is crucial (IMHO). I think you can sling and hand them out quickly enough to handle the crowd.
Price? Cost of dog+bun+.010 for condiment and all paper goods (wrap, napkin, etc) X 3 or you’ll be giving the product away.