I had purchased a refurbished Pixel 3 as a secondary device which turned out to be bootloader locked because it was from US. However, in general, it is still a good device for daily use and because it supports GSI in the secondary partition, it can be used for development even for later versions of Android. Thus, an old Pixel will do great for development.
Otherwise, if you can unlock the bootloader and load a custom ROM, then you can basically use any device to target the latest API for development, not necessary to spend a bucket load on the latest Pixel. Honestly, the only reason to get the Pixel is for the camera. Interface is also smoother on lesser hardware because of lack of bloated skins and optimisation. Otherwise, it doesn't stand out in other parameters.