Extremely difficult question to answer. It will mostly be justified by traction in a certain amount of time. If you receive a huge number of users in a year, this will add multiples to your valuation.

On the flip side, if you are ten years in with steady growth, the multiples will not be as high.

Industry matters, as well.

I'd say $50 million a year in gross revenue will definitely get you a $100 million buyout.

I personally have always found that 9 figure buyouts are generally reserved for people who don't want to be bought out. In other words, if you build a business because it interests you and you have the intention to stay at it for the long haul, you are more likely to get there than if you try to build a 100M business.

When I was less experienced, the thought of turning down a 3Bn offer was crazy. Now, I realise that I love my company and what I do and really don't want to lose that. This thinking makes a better company - no cut corners, always thinking long term, always focused on what is best for my business and not what will improve its valuation numbers.

Here you can find everything you need to know:

http://christophjanz.blogspot.com/2014/10/five-ways-to-build-100-million-business.html