Unless your garden is really huge, you should be able to get by with a lot less than $400. You are only keeping chickens out, so chicken wire is enough. A 6' tall, 165' roll around here is less than $50 at the farmers feed and seed. Posts can be small and quite far apart, like 6' to 8'. If fence posts seem high, check out treated 2X4's or even 4X4's at the lumber yard. Small common nails, like 6 or 8 penny, will hold the wire to the posts; pound halfway in, then bend over the wire. Easy to do even for this old woman, and cheap. You should be able to construct a gate with chicken wire and lightweight wood; treated 2X4's ripped with a table saw work well. You might want to cement the gate-holding post, and use something a bit more substantial like a 4X4 for that one post. An 8' 4X4 is under $5. I fenced my garden for the cost of one roll of chicken wire, but I had some old, small diameter posts and a few 4X4s lying around. It won't last 30 years, but then, neither will I....