Reassure me that your server does not only do witness but also does node RPC because for a witness server it's overkill.

Spec of mine (I have 2, the second is a backup/seed node/testing server) and it works well since 3 years ;)

CPU:Intel Xeon E3-1270v6
4 Cores/8 Threads  3.5 GHz/3.9 GHz
RAM: 32GB DDR4 ECC 2133MHz
HDD: 1 To SSD NVMe

If with 10,000 HIVE/month top 20 don't have their ROI there is a problem hahaha and for other things than witness, there is the Decentralized Hive Fund (DHF).

A tool that can help you in your calculation of your ROI: https://www.cutehive.com/witnesses.php

Starting under rank 60 you will win enough to pay your server, at my rank (active 72) I make 155 HIVE/month which pays one of my servers + part of the reimbursement for 3 years of losing money, maybe in 3 years it will be the turn of my 2nd server hahaha