For my hobby projects all the lumber I’ve bought in the past year is off the cull cart at Home Depot usually for 50-70% off. Yeah, some is a bit chewed up or bent or split, but usually very useable.
An example: $10 for a 5/4x6x16 pressure treated plank (I cut it in half) and a distressed 4x4x8’ Douglas Fir post that had a split I glued up:
This cut up 3/4” mostly oak veneer plywood was free:
makes up more than a 4x8’ piece…
All of the wood in these 2 rolling carts and the drawers (4 ft and 2 ft long) is made of 1/2” and 3/4” plywood and pine planks, I spent about $80 for all of it. The casters were $10/4 off of Woot and Amazon on sale. I got the knobs free. The expensive parts were the US made drawer slides by K&V: $25 a pair…
I go to my HD about 3x or more a week and check out the cull cart, stock up when I can, because I’m cheap. About the only wood I won’t buy is twisted, or moldy. And check out your local Habitat Restore for stuff. Used doors or windows might suit a shed or other project that doesn’t need new A1 parts.