Cloth pays for itself very quickly. I have used cloth exclusively with my now 5mo, and I calculated that using full time cloth nappies and wipes saves around $100 per month.
I have about 50 one-size-fits-all nappies (secondhand BBH fitted and tuttos seconds which were $13-14 each), which I spent about $500-$600 on. so they have already almost paid for themselves.
And you can either sell them or use them for subsequent babies.
If I didn't already have adequate nappies, I would definitely be buying the 4 packs as it's a great price for firsts.
Plus it's fantastic not having nappies in your bin or in landfill.