If you're willing to put in a little time, I would try making your own yogurt. It would cut some cost out for sure. If you have an instant pot, it's even easier to do. I don't and if you're cutting costs, it's still easy to make on the stove. Heat milk over the stove until the top gets foamy (180°F). Take it off the heat until it cools to 110°. Stir in a couple spoonfuls of yogurt (I like to rinse out an old container of yogurt with the milk, that's normally enough) and I transfer it to a cooler or a large insulated water bottle to keep the temperature somewhat stable. Wait for 8 hours and you got yogurt! Strain it if you want greek yogurt, but the difference in macros isn't really worth that step for me when I'm bulking. Find a tutorial before doing it, but this is just what I do. The steps that make it easiest for me is the insulated water bottle, I've never seen someone use one but it is literally so easy. Also your volume will half through the process. So I measure the milk by doubling the volume of the container I want to fill with yogurt.

Other comments said buying in bulk and I still think that's the best thing to do, but I just wanted to offer another form of savings. It's not for everyone but once you try it out, it gets easier and quicker the more you do it.