Dritz makes a Heavy Duty Snap Kit that comes with a metal post and a black "bowl" that you can hammer the heavy duty snaps with, without buying those expensive pliers. The "kit" is usually a couple dollars more than a pack of heavy duty snaps alone.
Sometimes I wish I had the pliers, though, because I feel like I could get a better fold on the snap posts. I've had a couple fall apart where I'm putting them through thicker material like my canvas belt. I also live in an apartment and I can't be hammering away at all hours of the night like I find myself needing to do.