Self-made millionaire?

I don't think it's hard to become a millionaire. I think it's a realistic goal and it can be achieved in a lot of ways. My way will be to create web-applications.

The Internet is a major market, it's a market of around 1 billion people. On the Internet creating something that people truly want won't only make you into a millionaire, it will make you into a billionaire, great examples on this phenomenon are Google and Skype.

The biggest issue is to create something that people want - just like Paul Graham preaches.

A plan to become a millionaire? Say we have around 100.000 users. Is it unrealistic that 5000 of them would pay $5 pr. month for some extra service? If this isn't unrealistic, then it's possible to become a millionaire in 1 years time (at least in danish kroner):

• 5000 * $5 * 12 = $300000 = 1.6 million kroner

In my opinion the above math isn't unrealistic, but it requires hard work and some luck. What do you think?