All the lumber in a house does not add up to what the furnace/AC costs. The big money in a house is the kitchen.
Windows and doors cost a lot more than lumber, plywood, osb.
FYI, the wholesale lumber market topped out a couple weeks ago. Plywood/OSB is still tight. Prices are just starting to come down. For example, the price of a 4x4-8’ #2 SYP from a sawmill went from a low of $350/mbf in March to a high of $1400/mbf last month. We can buy them today for $850/mbf.
2x4-16’ #2 Spruce was $400/mbf in March. Topped out at $1500. Today they are asking $1150. Prices are falling. They do not fall equally. Just like they did not go up equally.
This is what I’m waiting for. I have a lot of cabinets and shelves (and a wall) to build in my new shop/garage. I put it all on hold until this price bubble bursts, which I’m confident it will. But it may not go as low as it was.
Regarding price variability, the 1x6 “fence” boards I bought months ago to build our planter boxes cost $1.65. Now, they are $1.74. Really, no difference.