Prices in this area fluctuate a lot for the same type pipes. If you live in a smallish town, the road supervisor usually knows who has the best deal at any given time.
Not to be picky, but most folks in my neck of the woods would call what you are after "culvert pipe". "Field tile" at least here, refers to the perforated & corrugated stuff that is roughly 4" in diameter. The "drum" for your packer I would assume you will want in a larger diameter and thicker wall. So if someone asks or don't understand - calling it "culvert pipe" may help. Just understand that the metal "culvert pipe" your county may use has more of a "spiral" to it, while these heavy poly pipes are more "ribbed".....if you will, which will result in more of what I think you are looking for.