Yeah that many would cost you a bit, but DIY would be a lot of time and probably a bit of money to. Be sure to tally up all the true costs of you doing it yourself though, would be interesting to see the difference. When I bought 4 each of 3 different sizes the shipping was only like 8 bucks and the whole deal was like $60.21 or something. While DIY will hopefully save money, you won't be able to make a product that works as well, because that design with the cones helps guide roots that don't head straight for the air hole. So while you could puncture your bucket (or whatever you use) with a ton of holes, it still won't have the same dealy. I think if you are running an operation that takes twenty-four 3 gallon pots and a dozen half gallon pots, that it would probably just be better to go and buy them since they should perform better than a DIY version, and with that many plants of that size you should be able to make enough to buy them. I went to growers-inc and did up that order for you, they don't have 1/2 gallon though, they have .3 and .8 (as far as under 1 gallon goes) and so I went with the .8 for your order. They come from Salem, OR and shipping that much between them and Kent, WA would be $37. The whole order would be $299.13 while that may seem like a lot, it works out to about $8 a pot (which I think is worth it especially if you are growing that much).