It's a bit off topic, but the challenge there is similar to a reply I wrote elsewhere in this thread about clock speeds. Minecraft is almost entirely single threaded, which means that you could get a $400 Google cloud instance and still only be able to hold those three players. To scale past that you're going to need higher clock speed processors. Take a look at OVH's "GAME" series offering or any dedicated host with E3's or i7s.