It really depends. Quite a lot of witnesses are not really in this for money, so they do not really pay heed whether or not they're profiting and/or breaking even from their witness rewards.

If someone has a spare server they can turn into a witness node, that's a potential income. (i.e. if you were not spending anything, you're getting some witness rewards)

It also heavily depends on what the witness is doing, in general, to understand whether or not they're looking to break even and/or profiting.

I would expect witnesses ranked 80 or lower to potentially (if they are paying for a server on average market prices) lose money. As the witness rewards are probably not enough to cover the costs.

On the other hand, this does not mean someone in the Top 20 witness is swimming in money in most cases (arguably). They might be spending thousands of USD every month just to provide services for Hive users. (@blocktrades, for example, api.hive.blog is a cluster of hived and hivemind nodes, that is not cheap to do. Not to mention actual core development work without any DHF proposal whatsoever.)

This does not necessarily mean that blocktrades is a philanthropist. He just believes in the ecosystem and wants to contribute, paying out of his own pocket if need be or barely breaking even with witness income. If Hive was $5-10 USD, his and his team's work would pay off greatly.

Personally, I have been a witness for more than a year at this point, majority of the time I was a witness, Hive was averaging at about $0.12 per Hive. I was ranked ~60-80 during the year 2020. So when you consider my income, I was not breaking even at all and was paying out of pocket each month. I currently run several different services on Hive (one of them being api.deathwing.me, one of the most used nodes.) that require beefy servers that cost a lot of money per month to run. Thankfully, as of writing this post, I am witness rank 34 on the blockchain. If you look at my account history, you can observe that I haven't powered down once just until a month ago, and still, I only power down enough to cover costs for running my on-chain services.

All the rambling aside, the topic of "increasing rewards for post-Top 20 witnesses" has been discussed quite often. Maybe it'll work, maybe not. The main factor, always, is Hive price though. If Hive was $5, a Top 100 witness earning 2 HP a day from witness rewards could easily pay off their server costs. But for now, unless they have access to really cheap servers that are able to handle hived, witnesses ranked 80 or below probably do not break even. Considering they're running their witnesses though, they definitely trust in the ecosystem.