When I brew extract, I buy kits. I tend to get them from NB when they’re on sale. My LHBS actually just made up a couple of their own kits. I bought one on pure blind faith just to support the business.
When I brew all grain, I brew 3 gallon batches. I’ll occasionally buy one of the limited selection of kits from Northern Brewer, but basically I buy sacks of base malt and specialty grain by the pound from wherever is convenient.
I get US-05, Notty, and SA-04 from Amazon. Liquid yeast I get from the LHBS or I do without. Wildly inconsistent ship times made NB lose my liquid yeast business.
I sincerely wish hombrew ingredients would be a profitable business, but perhaps it would be better for us all input homebrew supplies were more of a mainstream market than niche.