Make a dedicated server profitable. Help! :D

Think Outside the box, What is it that the other servers don't do? Do more, and raise the prices just slightly.
Minecraft for example.
If you purchase a server host, You must create your buildings, configure your plugins, as well as advertise.
So why not offer a Set-Up service with your DDS? Charge them for the Set-Up additionally to the original price.

Team-Speak and Mumble aren't as widely used now that Discord is taking over. So I wouldn't waste money in them.
However, You could offer a Discord Service where you set it up for them, There are bots for it you can find anywhere making it more professional and clean.

But perhaps you could offer Advertising Services? Servers always need players, and players always need ads. This would possibly get you more customers as well. For example Create a banner with your website on it . Or they could pay an addition fee to have the website removed. Example: If your website was Example.com then make they're IP be Server.Example.Com

Offer a Free Trial coupon for about a month, This will allow people to actually get a feel for your services. Not to mention once you start something you want to finish, so perhaps don't allow them to download they're server files personally?

Offer a Premium Enjin Website, Its inexpensive but also handy to have with any server.

Hope this helps :D