The CPU is soldered to the mainboard and can't be swapped out on its own, unless I'm looking at it wrong on their website.
On this main board ($340):
https://frame.work/products/cooler-master-mainboard-case-and...
The CPU is worth $250 already.
You pay a $100 to get a swapable CPU on a laptop which is guaranteed to be compatible.
You might value or not this feature, and that's fair.
But I do value it a lot.
Even on a tower, matching a board and a CPU is not a given. On a laptop, forget about it.
As for the costs: Yes the mainboards on frameworks website currently cost about 500-1000€, new laptops using those cpu's are tend to be a bit more expensive than just those parts, so you are saving a bit of money there. But in my opinion that is not the main selling point. The fact that you get a high quality, long lasting, well supported laptop from a company that respects it's customers and their problems coupled with the fact that it is just environmentally better is the main selling point.
Yes currently you pay extra for those benefits. You have to choose if those things are worth more money than the next 3-year throwaway laptop.
Btw: I am a very happy user of a Framework 16 as my gaming machine. So my opinion may be biased ;)