It's not just the chassis, it's also the screen, storage, RAM, ports, speakers, battery, and so on. And there is lots of demand for old mainboards, they sell pretty quick on Ebay. More sustainable to only buy and sell the part you need than the entire laptop, especially factoring in shipping costs. Plus the mainboards can be used like a mini PC.

The place where the framework design really pays of is the ability to trivially swap ports. most laptops have the usbc on the motherboard so a warn out connector is a $800 repair. Even those that have separate daughterboards for IO typically will be a ~1hr+ take everything apart to fix. With a Framework, replacing a worn out connector is ~$15 and 15 seconds.

You can take the old mainboard and slot it into a cheap case and run it like a slim pc.

Here's the thing: this argument you are making has made the assumption that Framework laptops are a huge compromise versus just buying a regular laptop. This line of thought assumes we are giving up something to get modularity and repairability, and that value proposition doesn't make sense compared to selling your used laptop and buying a new one from a traditional manufacturer.

This argument is flawed for two major reasons:

1. You can do perform the exact same non-modular ownership experience with a Framework laptop. It's just a regular laptop. You don't have to use the modularity or repairability at all. You can treat it like any other laptop and sell it when you're done and buy a new one.

2. Framework systems are getting increasingly competitive over time. The 13 Pro is quite competitive in its field and is one of the best options in its size/price/use case category. What other Panther Lake laptop is offering a drastically superior value? I'm looking for a portable system with long battery life (Intel Panther Lake) that is primarily for text work and coding while being capable of decent gaming on the side (Nothing crazy, the X7 Panther Lake chip gives me enough GPU usage for my needs). I did a ton of research and basically narrowed down my list to the ThinkPad X9 15p Aura Edition and the ASUS Zephyrus G14. Last I checked the ThinkPad was roughly 10% cheaper with an equivalent spec, the OLED screen is lower PPI and worse for text work, the battery lasts 5 hours shorter performing office productivity tasks (Just Josh's testing methodology), and the webcam is/was broken in Linux. The 15" screen is almost exactly as tall but it's wider, I call that neutral to negative for backpackability (3:2 screen ratio is lovely). On the plus side, the ThinkPad does push more power to the CPU/GPU, improving overall performance compared to the Framework. The ASUS Zephyrus is only in the same price category if I buy the 2025 model which has more compromises compared to the current model, especially for non-gaming battery life (no Panther Lake). Even if I open up my wallet to buy the 2026 model, I am missing out on things like a haptic trackpad, and of course, if we think Framework's support/repair experience is lacking, we don't even want to talk about ASUS RMA horror stories.

Other Panther Lake options with the X7 356H:

HP Omnibook 7 16, $1419: too big, off-center keyboard with numpad (don't like), low PPI display.

Acer Swift 16 AI, $1549: too big, off-center keyboard w/numpad, 16GB soldered RAM, non-premium chassis, no charge port on the right side, loud fans

LG Gram Pro 16, $2999: more expensive than the Framework 13 Pro with same specs

ASUS ExpertBook Ultra 14, $3599: more expensive than the Framework 13 Pro with same specs

Of course, Framework's other systems like the 12, 16, and base 13 are not really as competitive as the 13 Pro in my mind, but still, I think there's this whole vibe like Framework buyers are really giving up a lot of basic laptop things and paying way more to get modularity. This was much more true 5 years ago, not so much today now that Framework has been selling in higher volumes and refining their designs over the years.

I agree with your point on chassis/mainboard matching but wrt "putting the old mainboard on a shelf," Framework does have some cases for bare mainboards made by coolermaster and I think the 3d printing files are available.