per side. for example, you could have (and many large individual/institutions did) enter an order to buy 10k contracts of xyz and it would only cost 10. to exit it would cost 10.
there may be other ways to hedge, spx options, es options that may be cheaper not to open up a can of worms here.
+1. or look into e option for a low flat per trade fee and 0.10 per contract if you're trading a lot of contracts at once.