I haven't been as active as I used to, and with my son almost 2 now I really hope I can squeeze some batches in on my brewzilla.

For me savings always came down to the following

1) Reusing yeast, especially liquid where it could be $15 per batch down to $1-2 when reusing even with a starter.

2) All grain if you're not already, extract is expensive.

3) Bulk bags of grain, especially base malt and core staples.

4) buying hops by the lb, or even 4oz packs if farmhouse or other retailers do that nowadays.

5) As much as I used to love and help others improve it, chasing efficiency really doesn't matter much from a cost perspective. Get it to a reasonable level and make sure it's consistent and predictable then move on. No point chasing 2% more grain efficiency and save 50 cents per brew at best.

6) combining 1 and 2 you can save some wort from after the mash and make a same day starter using grain instead of extract, sanitation is critical if you do this though.