The last new one I bought in 2018 I actually paid the same price for it than when I bought my first one in 2015, so it is one of those few computer accessories that significantly increased in price over its course rather than decrease.
If you cannot see the P2415Q degrading and/or being generally crap in any metric (EXCEPT DPI) when compared to even the non-IPS black Dell monitors from this decade, you are simply blind. They are early HiDPI-revival-era panels, and it shows.
Some of the newer IPS black panels are so good that it is tempting to just take the DPI hit and go 27''... albeit with care as it seems Dell has decided this last year to put some filter that further increases blurriness.