To be a witness is to be commited to the Hive blockchain. It is not profitable to be a Witness on a lower rank. I would say only the top 20 have the remote possibility of maybe making a return on their investment, and even them, because the run other services for Hive, may not make it! So maybe even some top 20 may not get back what they invest in infrastructure back as HIVE Power.
My server
My server is not expensive, considering its resources, it was actually a great deal. Under 100 Euros a month for an extremely powerful hardware. Now that the Euro and the US Dollar are hovering around 1-to-1 it it means under 100 USD a month for a very powerful server. I can run all my Hive stuff and it doesn't even consume 20% of the resources, which means I am relatively safe if the network activity goes up unexpectedly!
My "earnings"
Witnesses get "paid" in HIVE Power to produce blocks, but I put that in quotes because, personally, I don't plan on powering down. I have enough HBD to keep my witness server running for over 1 more year, so I probably won't need to power down.
@quochuy publishes a monthly report on witnesses earnings. I am positioned at #102 on the rank of witnesses, at the time of writing this, but I am #88 on the active witnesses rank (many witnesses above me are not producing blocks regularly!).
The witnesses ranked at #81 and #82 are making just under 100HP a month, at the current exchange rate that would be around $40 a month
Conclusion
My server costs me around $95 USD a month, and by producing blocks I would, optimistically, get just under 100 HIVE Power a month. At the current exchange rate that is $40 USD.
Even if HIVE doubles in price, if it goes up 100%, I would still make under $90, which means I would still not make it back what I need to invest on infrastructure.
Am I complaining? No! Being a witness is awesome and I am proud of being part of the history of blocks on this blockchain.
It would be nice if HIVE went up to 1 US Dollar, then I would know that for every single dollar I spend on my server I am actually "buying and powering up HIVE". It would be like buying HIVE indirectly! I am buying HIVE and powering up it on a weekly basis anyways, being a witness is just part of the process.