Or you could just buy a MacBook Air for like $900 (or one of the windows snapdragon machines, but it you care about avoiding Intel I’m assuming you want Linux and doubt the support is as good as asahi on Macs)
In that lens, the config I played with (before ram prices surged) ended up around $2200 and it felt nice knowing I could upgrade the GPU down the line for $400 instead of pondering if I can last another year or 2 before things fall behind. As long as the chassis and screen is solid I can deal with some compromise for that value.
Even on desktops where constraints are easier, piecemeal hardware upgrades of anything but storage and ram has never been worth it or done much to extend system lifespan.
Edit: though it should be said that what I think is good might be a far cry from you think is good. I did use a Thinkpad X13s as my primary work machine for 6 months, though.
I would be very surprised if many frameworks are upgraded ship of Theseus style for decades, or if the total cost of ownership (and even ecological impact, most of the nastiness is going to be the electronic internals, not the metal casing) is lower than for someone buying a more integrated laptop ever 5-6 years.
Hard to say. If people boast about a ThinkPad lasting a decade, I see no reason (post Moores law) that this can't last that long. The only think not obvious on how to replace is the screen and speakers.
A good test would be to work out what's the oldest in-use Framework (which should be one of the first, if not there's an build quality issue) and see how many upgrades were needed to keep it functioning compared with similar era machines from other manufacturers.