Easy answer
The cost of running an MMO? In United States Dollars?
ITS OVER 9000 (dollars)!!!!!
Useful Answer
Scope of question
So, dividing your question up into chunks, you seem to want to know about the costs of:
- Development (making the game)
- Marketing (making people aware of the game)
- Infrastructure (base cost of server hardware and supporting infrastructure)
- Infrastructure maintenance (recurring costs in electricity, parts replacement, rent, etc.)
- Operating expense (cost of patches/updates/moderation)
For the sake of simplicity, I'm going to play a little bit fast and loose with the numbers here--these will be mostly back-of-the-envelope informal estimates, informed by common sense, my engineering background, and my location.
I'm going to err on the side of being a small developer, and I'm going to bend rules to get you your MMO. You should thus consider this to be a very conservative economic assessment (you will probably end up spending more) and a very liberal social assessment (you might end up in prison with some of my shortcuts).
I'm going to avoid assuming supermen developers and exotic product designs, and instead assume a conventional MMO such as Asheron's Call or WoW and merely highly-motivated developers (which is still a generous assumption).
Project scope estimate and assumptions
So, let's throw out some numbers to get started. These may or may not be reasonable, but they give us a place to begin.
- Development time: 2 years. (this is about how long Minecraft has been in development, and about the total amount of time it took to create Project Volucris, an MMO based on Xenimus)
- Development rate: Full-time work. (you aren't working full-time, you aren't working)
- Running time: 4 years. (people still play Asheron's Call and Ultima, so not unreasonable)
Cost the first: Development
So, let's consider the costs of development. I'm going to keep a running total for you.
People
So, we know that zero people will get no work done. Minecraft was done by 1 guy, WoW by hundreds. We expect to fall somewhere in that range. We support specialization, so we expect to have people dedicated to one field (some overlap, perhaps). We need at least one coder and one artist. This, however, will be an MMO, and so we need someone to babysit the servers; add a sysadmin.
Except, this doesn't cut it. You want some amount of redundancy in case somebody gets sick, so double all of those. Especially for programmers, you really need somebody to call you out on design decisions and motivate you. So, 6 people. More artists are better (content creation really does scale linearly!). So, 8 people. A third programmer wouldn't be a bad idea either, especially if you need to farm out grunt work while doing design. So, 9. And a tools programmer is going to be really important--but let's pretend that could be your second sysadmin.
So, 9 people. Let's assume they are motivated/deluded into doing this for two years, and so are willing to work at minimum wage for the duration of the project. Living wage where I live is roughly $18k a year; these guys are also all-star developers, so let's given them a $7k bonus on top of that.
(Incidentally, this is paying them peanuts compared to industry work)
(also incidentally, this is assuming we are treating them as contractors, and so have avoid the full cost of things like health insurance, HR overhead, etc.)
9 people x $25k per person per year x 2 years development = $450k
People Cost: $450 000. 00
Grand total: $450 000. 00
Software
Operating systems
Let's save our money and use Linux for everything, and assume that we can test on our home machines, or that the users can magically provide beta-testing for us. Or, even better, that we pirate copies of Windows or OSX, or scavenge license keys off discarded equipment.
*OS Cost: $0 *
Art tools
Let's use the GIMP or Paint.NET for our 2D art, and Blender/Wings/Sculptris for our 3D art. Or, we can get Adobe CS5 and 3DStudio Max 2011 with the PirateBay discount. The end user doesn't know/can't tell, and we can probably mask the origin of the assets from inquiry.
*Art tools Cost: $0 *
Code tools
We can legitimately use GCC/Visual Studio Express/Eclipse for free. If we really need to have the fancy ultimate/pro/whatever editions, back to the Bay--just remember to strip your executables afterwards.
*Code tools Cost: $0 *
Software Cost: $0. 00
Grand total: $450 000. 00
Hardware
Development Hardware
Let's not assume that you need insane next-gen tech, and let's not assume that you ask everyone to just bring their home machines to work. So, a couple of minutes on TigerDirect show several systems for under $500. I'll assume you spend a full grand anyways, which could be for storage, RAM, video card, or whatever helps that particular developer.
$1k per box per developer x 9 box-developers = $9k
- Developer Hardware Cost: $9 000. 00 *
Server Hardware
IBM has some great hardware for many tens of thousands (hundreds of thousands!) of dollars. Let's Google this, and use cheap normal components. Let's again use the $500/box metric from above.
Second Life has over 2000 servers. We'll use that, since you asked for Second Life as an example.
2000 servers x $500 per server = $1 000 000. 00
- Server Hardware Cost: $1 000 000. 00 *
Hardware Cost: $1 009 000. 00
Grand total: $1 459 000. 00
This is before you have marketing (zero to millions, depending), maintenance, or anything else. This is just development and the server hardware costs. If you want me to continue this analysis, please mention it in the comments.
MMOs are expensive to make.