As far as spectating goes, I'm 99% sure it's free. Just show up and watch paintball and do some shopping in the vendor area.
Pro field grandstands might be a bit of money. I don't think they are but if so I'm sure you'd be able to buy the tickets there no problem.
I used ta do a little but a little wouldn't do it
So a little got more and more
I just keep tryin' ta get a little better
Said a little better than before