

The Pocophone F1 was 300 EUR when it launched. Sure you can buy used phones for much cheaper than new ones. If you want to get a cheap Sailfish OS device, get a used Sony Xperia 10 II for 50-80 EUR. Yes, it is a tad worse in performance for the CPU (and much worse for GPU, in case you care about that) than the F1 but there goes your “10x” difference, when one is not comparing apples and oranges. Or you go for a community supported phone like the Mi Note 10, which you can find for 120 EUR, comparable SOC performance but much better screen and dramatically better camera than the F1.
Btw how is the camera functionality, VoLTE functionality, battery status, etc on such a device with postmarketOS? Honest question, because according to postmarketOS documentation, there is not a single device that is listed to have all the basic functionality, other than the Librem, a device with weak hardware sold today for 799 USD.
Tinkering is not black and white but a spectrum. That is why LFS, Gentoo, Arch, Fedora, Linux Mint etc all have their justification to exist. Sailfish OS gives a a pretty functional phone out of the box but allows you to tinker around if you want to, not to the extend a Postmarket OS would but UI aside, you can get down deep and dirty if you want to, as far as I understand. In a similar way, I don’t think one should get Sailfish OS over postmarketOS, there is a place for both. That Sailfish OS costs you 10 times more, necessarily, is just false information.
The premium of the new Jolla Phone, over Chinese competition is maybe 2-3 fold. New vs New. Look at other dedicated Linux phones and that is quite common, simply because small production run phones can never compete with Chinese mass production phones on price.

If you operate that within the EU, you better know what you are doing, hope it never gets leaked, or don’t do half of what you are implying here.