The problem your overlooking is not just the upgrade vs new cost, but also the parts issue.
Buying a brand new Framework tend to be more expensive then a ~ Chinese Laptop.
*New vs Upgrade*
In general, you can sell a second hand laptop at around 50% of the original price, about 2 years down the line (assuming you did not damage it).
So a new upgrade will be 50% cheaper. For that you tend to get (depending on the generation jump), more storage, more memory, potential better screen, faster CPU.
While a Framework upgrade may mean you gain a new Motherbord+CPU for the price of that equivalent laptop. But here you run into another economic issue. Sure, you can transplant your 2100mhz memory but what if 2660 is the standard. So you CPU upgrade is going to get throttled.
*Changes*
What if memory changed with a inner generational. So now that memory you had before is useless. You can recover some value, but are still forced to buy the generation memory.
That wifi card, 5e ... great, but now your getting maybe 6 standard in a new laptop.
Also do not forget, your laptop will have more wear and tear vs a new device. Keyboard may become a issue. Your oled screen may have reduced coloring after 1 or 2 generation of usage (oleds suffer from high screen brightness, and laptop are more often in locations like outdoors that run at 100% brightness).
*Compatibility*
What about compatibility? Maybe you had a Intel based Framework laptop, with a intel wifi card. The problem is, some intel wifi cards need specific intel instructions onboard the CPU. So now you upgraded to AMD but your wifi card becomes useless.
Yes, a new laptop is rolling the dice regarding defects or other issues. But so is upgrading a framework. The problem is, your getting all the not so fun parts of a desktop's upgradability, without the cost saving potential of a desktop.
*Resell issue*
Selling your framework memory, wifi card etc will not be a big issue. But the moment you want to sell a older part, now what? Great that you upgraded from 1080p screen to 4k by yourself, but who is going to buy your 1080p screen? Your at best looking at a small market of framework owners, and a even smaller market of framework owners that need a new screen (maybe to replace a damaged one).
What about the bezel changes? What about the keyboard? What is your buyers market. Sure, maybe you can sell your old MB/CPU but even that is a VERY specialized market of people, who maybe need one to repair their framework, or want a custom nas (cheaper to just buy a mini-pc from the dozens of Chinese brands) or the few people who run a very old framework mb, and upgrade (what about their selling 2+ generation old MB/CPU combo).
*Buyers*
Framework really is for people who do not like to change laptops / get used to new ones, and who have no issue taking in the extra costs of those upgrade potential. But then again, i see people running macbooks M1's still (darm good laptops), for 5 years. They did not need the upgrade path.
It really depends on you, what you really value. But from a economic point of view, your not going to be cheaper in the long run with a framework, and that is not the selling point also.