Monthly Cost $9.99-$14.99 One-time server setup + storage
The problem is that's not the monthly cost because (in addition to running a server not being a one time thing, they need maintenance) it's not including the cost to actually buy all the music:
Digital purchases (Bandcamp, iTunes, Amazon, etc.)
For me:

https://www.last.fm/user/ikt123/listening-report/year
Paying for 7808 albums in 1 year is unfeasible, so this is not a replacement for Spotify for me, it could be though if you only listen to a tiny amount of music, at current rate of $15 a month for me, it's equal to like 1 album and like several smaller singles, if this is all you listen to in a month go for it.