And the fact of the matter is that in 2026, all electronics has gone up, not down, and sought-after GPUs have gone up in price in the used market.
They are selling on EBay for over $20k, used.
The 0-reputation account in Spain selling an M3U 512GB for $4200 is 100% fraud.
Doing this particular one is definitely expecting the market squeeze to continue. "Worst case" is back to more "normal" depreciation. Where I'd expect to only be able to recoup more like 18k. But... if you look at GPU prices the last 3 years... it's not a crazy assumption that it won't drop that fast.
iPhone example since those are easiest to find in quantity: new iPhone 16 Pro Max for $1200, Gazelle would want $866 for "execllent" condition. Lost ~28% for one-model-back. iPhone 15 Pro Max, though: excellent priced at $667 here, only down another 23%, and gives you basically half-priced-upgrade if you can sell it for that and roll into the newest.
So to have never-more-than-one-model-old rough estimate at today's value-holding you'd be out $3600 for three new phones, with getting 1732 of that back, or 1868 for it (with a $334-per-year incremental cost of upgrade).
For never-more-than-two-models-back you'd be out $2400, getting back $866, for net $1534 spend, with a $167 incremental per-year upgrade cost once you buy the first one. Pretty good if you keep the phone in excellent condition and are happy to budget a bit over $10/month to be on a every-two-year upgrade train.
Well, you'd also eat the tax...
https://buy.gazelle.com/products/iphone-16-pro-max-256gb-unl...
https://buy.gazelle.com/products/iphone-15-pro-max-256gb-unl...
I would absolutely not count on that, if and when it drops it will drop hard.
Computers depreciate because they are obviously being supplanted by newer better models—until they become vintage and then move into collectibles.