I buy hay by the bale- and I keep it stored in my garage wrapped in a large cotton blanket- and the bale is in our wheelbarrow so it is not on the floor of the garage. So it stays clean and dry. Obviously buying hay by the bale will vary depending on your source- but I was able to find 3rd cut grass hay for $4 a bale.
I am in in Michigan so from my understanding at least in my area- hay is only grown and cut during the “growing season”- summer and fall I would think. So it is reasonable for hay to be stored for a year or so.
I was buying the Oxbow and Zupreem hays and once I started buying the larger quantities in the LARGE bags I noticed there was a quality difference- the softer hay seemed to be in the small bags- easier to package I guess. And I am not joking- on one of the larger bags it was clearly the end of a regular shaped bale of hay. And considering how much I was paying for a bag!! i decided to check out local hay bales and have been very happy.
I do like my bunnies to get variety- so I buy the mini bales from BinkyBunny Store and use that as “treat hay”. Schroeder and Cotton especially love the oat hay and are so happy when I toss a small handful in their litterboxes. They immediately snarf down all the treat hay. The nice thing about BinkyBunny hay is that the quality is ALWAYS consistent I have noticed. I also use the BB hay for putting in brown paper lunch bags with other goodies mixed in- roll up the bag punch a few holes into it and give them to the bunnies so they have to forage. (I read about doing that here on this site).
Personally- for all my pets I like them to be exposed to a variety of food or treats- I never want my pets so used to one thing that they will not eat anything else.
Schroeder is a “hay monster” he digs ALL of his hay out of the hay bin and into his litterbox. So at least this way I don’t stress about throwing out a ton of hay when I clean his box. If I was paying what I used to for bagged Timothy hay- I would be worrying about the cost of what I was throwing away.