I'm in the process of converting my herd over to oats. However, when feeding pellets, I feed Small World Complete Rabbit Feed. I think it's 16% protein and doesn't contain any corn and after tax I was paying around $8 for 25#. On average, my bucks get between 1/2 cup to a full cup of pellets, and all my does get 1 cup unless they're nursing (and the amount they get depends on their condition). They also get free choice alfalfa cubes that are between 16-17% protein depending on the brand I get and I free feed grass hay (usually orchard grass is all I can find up here). Lastly, I also top dressed with BOSS, mana pro, and bird seed as needed.
Right now, though, I'm converting over to a grain mix that contains whole oats, barley, wheat, and shredded (molasses free) beet pulp. They are still getting free choice cubes and hay. During the winter I intend to step up the usage of BOSS since it snows, but it will depend on how everyone's doing. All of my bags of oats and pulp run me about $16 for each 50# bag, but I anticipate feeding a lot less. I'm already noticing that the kits are putting on weight a bit better, and everyone all around seems to be satiated a bit better.
I also feed greens as I can get them. Right now they're chowing down on some sunflower leaves/stalks and rosebush branches that I brought down when we moved. I also have plenty of dandelion (though that's starting to slow down now that the weather is getting cooler). I've also taken to feeding them any safe, raw, produce that I have after preparing meals.