I get 4" square pots from a hydroponics store for $0.42 ea, which may not be the cheapest, but it's convenient. I can use them over and over, so I haven't sweated the cost. I've been getting no.1 ("1 gallon") pots from an eBay supplier for $0.24 ea. Add about $16 for shipping, and they're $0.40 ea. That hydroponics store wants $0.96 ea for the same pots, and Home Depot was somewhere in that same area. They are taking advantage of people not doing their homework. I don't think my local Armstrong Garden Center (a chain in Calif.) has these pots, but, then, they don't have much of anything useful to me.